Crystals doi: 10.3390/cryst16090589

Authors: Shiyang Hou Runsheng Zheng Chenghang Yang Xiaoqing Liu Yangyang Liang Qingbo Li

High-index 4H-silicon carbide (4H-SiC) provides a larger waveguide k-space than conventional glass and is therefore attractive for wide field-of-view (FOV) diffractive augmented reality waveguides. However, the angular response of a slanted grating is asymmetric. For one grating-vector direction, the diffraction efficiency remains high over a wide positive-angle range but decreases rapidly at negative angles, leading to nonuniform image brightness over a broad field. Reversing the grating vector reverses this response. The field is therefore divided at 0°, with the positive and negative FOV channels assigned to two mirror-related slanted-grating domains with opposite grating vectors. The grating parameters for the red (648 nm), green (548 nm), and blue (448 nm) wavelengths were optimized separately using particle swarm optimization. Their angular diffraction responses were calculated by rigorous coupled-wave analysis and then introduced into Zemax for system-level ray tracing. At 548 nm, the optimized 4H-SiC, n = 1.8 glass, and n = 2.0 glass gratings provided effective angular bandwidths of approximately 88°, 31°, and 37°, respectively. Under the same 4H-SiC material and system conditions, the +G/−G arrangement reduced the root-mean-square (RMS) irradiance nonuniformity from approximately 40.3% to 32.8% and increased the effective fill factor from 40.8% to 61.5% compared with the single-+G configuration. In a separate system-level comparison, the optimized n = 1.8 glass and 4H-SiC models yield RMS irradiance nonuniformities of 44.0% and 32.8% and effective fill factors of 46.1% and 61.5%, respectively. These results connect the broad angular response of the optimized 4H-SiC grating with the system-level balancing produced by opposite grating-vector assignment. The optimized grating parameters and detector-plane response maps also provide a computational basis for subsequent fabrication and experimental validation of the proposed 4H-SiC waveguide design.

Crystals doi: 10.3390/cryst16090588

Authors: Luxiao Sang Yujing Tang Yunsheng Lin Bolin Song Haitao Zhang Tengteng Li

Flexible perovskite solar cells (F-PSCs) exhibit broad application prospects due to their lightweight and bendable properties. However, uneven substrates and thermal–mechanical deformation during bending hinder the growth of high-quality perovskite films. Meanwhile, stress accumulation at the interfaces of flexible devices aggravates carrier recombination, resulting in deteriorated device performance and stability. Thus, we construct a poly(methyl methacrylate) (PMMA)/[1,1′-biphenyl]-4-carboxamidine hydrochloride (BPhADCl) composite modification layer to synergistically optimize the performance of F-PSCs. Specifically, PMMA can passivate interfacial defects and buffer bending stress. BPhADCl enables the in situ formation of 2D perovskite as nucleation sites to induce the growth of high-quality films, and the formed 2D/3D perovskite heterojunction can block moisture erosion and improve device stability. The optimized F-PSC delivers a champion power conversion efficiency (PCE) of 24.33%, remarkably higher than 20.71% of the control device. After 5000 bending cycles at a bending radius of 5 mm, the device retains 83% of its initial PCE. Moreover, the unencapsulated device maintains 91% of its original efficiency after 1100 h storage under ambient conditions.

Crystals doi: 10.3390/cryst16090587

Authors: Haiqing Xu Zhihong Zhang Huaijin Zeng

The high-value recovery of valuable components from spent LiFePO4 (LFP) batteries is of considerable significance for both resource recycling and environmental conservation. This study systematically investigates the simultaneous sulfuric acid leaching of Li, Fe, and P from spent LFP cathode materials, integrating process optimization with kinetic analysis. The effects of acid concentration, temperature, and stirring speed on the leaching behavior of Li, Fe, and P were evaluated to elucidate the underlying kinetic mechanisms. The results demonstrated that under optimal conditions—namely, a sulfuric acid concentration of 2.0 mol/L, a leaching temperature of 60 °C, and a stirring speed of 300 r/min—the leaching rates of Li, Fe, and P all exceeded 99.5%. Kinetic analysis revealed a diffusion-controlled leaching mechanism well described by the Avrami model, with a selective dissolution sequence of Li > Fe > P. The leaching of Li, Fe, and P exhibited apparent activation energies of 9.56 kJ/mol, 14.83 kJ/mol, and 12.82 kJ/mol, respectively. These findings provide theoretical support for the leaching and resource recovery of Li, Fe, and P from spent LFP cathode materials.

Crystals doi: 10.3390/cryst16090586

Authors: Duman Askerzhanov Nurzhan Serikbekuly Bauyrzhan Rakhadilov Zarina Satbayeva Aikyn Erboluly Vladislav Kots Zhanel Bakyt Aidar Kengesbekov Ainur Zhassulan Rinat Kussainov

HVOF coatings based on tungsten and chromium carbides are widely used in aerospace, energy, and oil and gas industries. However, the selection between the wear resistance of WC–Co and the corrosion resistance of Cr3C2–NiCr is often hindered by a lack of systematic data on the effect of powder particle size. In this study, WC–12Co and Cr3C2–NiCr coatings were deposited onto 12Kh18N10T stainless steel substrates by HVOF spraying using three particle size fractions: <20, 20–32, and 32–40 μm. Individual spray parameters were selected for each material to ensure high-quality deposition (standoff distance 350 mm, one pass for WC–12Co; 250 mm, two passes for Cr3C2–NiCr). The influence of powder particle size distribution on coating properties was investigated using a comprehensive set of methods, including scanning electron microscopy, X-ray diffraction with Rietveld quantitative phase analysis, microhardness testing, tribological testing, electrochemical measurements, and numerical modeling of particle in-flight motion. It was found that the 20–32 μm fraction is optimal for both materials. Different degradation mechanisms were identified: for WC–Co, decarburization of WC with the formation of W2C and η-phases dominates (maximum for the <20 μm fraction); for Cr3C2–NiCr, oxidation and carbide dissociation prevail (in the <20 μm fraction—13.7% Cr2O3 and 38.6% Cr7C3), leading to low coating thickness (~16 μm) due to loss of ductility and wettability. Numerical modeling confirmed that the high velocity of fine Cr3C2–NiCr particles (~680–720 m/s) does not compensate for their overheating, whereas for WC–12Co all fractions have velocities above the critical threshold, but coarse particles (32–40 μm) give porosity up to 3.15% due to insufficient deformation. Corrosion tests showed that under spraying conditions optimized for each material, the Cr3C2–NiCr coatings (corrosion rate 0.066–0.102 mm/year) are an order of magnitude superior in corrosion resistance to WC–12Co coatings (corrosion rate 0.353–0.651 mm/year), owing to the passivation of the γ-Ni(Cr) matrix; for WC–Co, the main protective barrier is provided by the structural density.

Crystals doi: 10.3390/cryst16090585

Authors: Zi-Bo Zhang Su-Ming Jing Tian-Yi Wen Yi-Wei Zhang

Improving the energetic performance of established explosives through rational structural modification provides an alternative strategy for the development of entirely new energetic molecules. In this work, bromine substitution was employed to regulate the solid-state properties of TNT derivatives, and two compounds, 3-bromo-2,4,6-trinitrotoluene (3-BrTNT) and 3,5-dibromo-2,4,6-trinitrotoluene (3,5-BrTNT), were synthesized and characterized. Single-crystal X-ray diffraction revealed that different bromination patterns lead to distinct crystal structures and packing characteristics. Electrostatic potential analysis and Hirshfeld surface analysis further revealed that bromine substitution modifies molecular surface characteristics and intermolecular contact distributions within the crystals. Compared with 3-BrTNT, 3,5-BrTNT exhibits a higher crystal density of 2.312 g cm−3 and improved calculated detonation performance, with a detonation velocity of 7915 m s−1 and a detonation pressure of 31.86 GPa. Meanwhile, both brominated derivatives exhibit reduced impact sensitivity compared with TNT. These results demonstrate that the bromination pattern, rather than bromine incorporation alone, plays an important role in regulating crystal structures and energetic properties. This study provides insight into substitution-pattern-controlled crystal engineering as a strategy for optimizing TNT-based energetic materials.

Crystals doi: 10.3390/cryst16090584

Authors: Detlef-M. Smilgies

Low-symmetry triclinic lattices, as formed by molecular thin films, are conveniently characterized by grazing-incidence wide-angle X-ray scattering (GIWAXS). These films are often highly textured with a specific crystallographic plane (HKL) parallel to the surface and thus form uniaxial powders. A classification scheme is presented that lays the groundwork for determination of the surface unit cell and indexing such complex scattering images. After identifying a first surface unit cell, methods are discussed for normalizing the lattice constants and further reduction of the unit cell.

Crystals doi: 10.3390/cryst16090583

Authors: Ping Zhang Jingxi Tan Jiebin Chen Huiru Liu Xiaohuai Wang Xiang Wang Chen Ma Shaoxiang Sheng Lan Chen Youming Lu Yun Li

By precisely controlling the growth temperature and coverage, we successfully synthesized a highly ordered zero-dimensional (0D) Sb18 nanocluster and a one-dimensional (1D) Janus Sb nanochain on the Ag2Sb/Ag(111) surface. Using scanning tunneling microscopy (STM) in combination with density functional theory (DFT) calculations, we characterized their atomic structures and found that the alloy substrate plays a significant role in stabilizing these configurations. Our findings not only demonstrate the feasibility of controllably synthesizing low-dimensional Sb nanostructures on metallic substrates but also provide valuable insights into their growth mechanism.

Crystals doi: 10.3390/cryst16090582

Authors: Julian Polle Florian Mai Marcus Layh Verena Spiegler Marian Hebenbrock

1,10-Phenanthroline derivatives are versatile ligands whose structural and biological properties can be tuned by targeted functionalization. Here, a series of 2,9-dihalogenated 1,10-phenanthroline derivatives and their corresponding 5,6-epoxy-5,6-dihydro analogs were synthesized and characterized. Single-crystal X-ray diffraction experiments reveal pronounced substituent-dependent packing motifs. While 2,9-diiodo-1,10-phenanthroline forms a sandwich-herringbone arrangement dominated by short I···I contacts, the phenanthroline epoxides exhibit π-stacking combined with C–H···O and C–H···halogen interactions. For the brominated and iodinated epoxides, additional halogen···halogen contacts generate extended supramolecular networks. Biological evaluation in selected cell lines showed that both halogenation and epoxidation reduce the cytotoxicity of the parent phenanthroline scaffold, whereas no significant effects on Pseudomonas aeruginosa growth or biofilm formation were observed. These results demonstrate how simple structural modifications of 1,10-phenanthroline influence both solid-state organization and biological activity, providing insight into the role of halogen substituents and epoxide formation in phenanthroline-based systems.

Crystals doi: 10.3390/cryst16090580

Authors: Daulet Sergeyev Gulbanu Serikbayeva Ainur Duisenova

Structural defects provide an effective means of tailoring the electronic and optical properties of two-dimensional transition-metal dichalcogenides. In this work, the structural, electronic, and polarization-resolved optical properties of pristine WS2 and WSe2 monolayers and their stoichiometric trefoil-like rotational reconstructions were investigated using density functional theory. The reconstruction was generated through a local 60° bond rotation without removing or adding atoms and therefore differs fundamentally from the experimentally observed chalcogen-deficient T1(3DV) defect. Electronic-structure calculations were performed using the PBE-GGA + U and SOGGA approaches, with noncollinear spin–orbit coupling included in the latter, while the optical response was evaluated within the independent-particle Kubo-Greenwood formalism. Structural relaxation revealed two distinct regimes. In WS2, the reconstruction produced a largely compensated redistribution of W–S bond lengths, with the mean distance remaining nearly unchanged, whereas WSe2 exhibited a net expansion of the W–Se coordination network and substantially stronger out-of-plane buckling. The reconstruction introduced additional W 5d–chalcogen p states near the band edges and markedly reduced the electronic band gaps. For WS2, the gap decreased from 1.87 to 1.55 eV within DFT + U and from 1.96 to 1.46 eV within SOGGA. A substantially stronger response was obtained for WSe2, for which the corresponding gaps decreased from 1.533 to 0.751 eV and from 1.657 to 0.645 eV. The reconstructed monolayers exhibited pronounced optical anisotropy, red-shifted absorption edges, spectral broadening, and additional low-energy in-plane optical transitions. These effects were particularly strong in WSe2, where the calculated optical response extended into the near-infrared region. The results demonstrate that the electronic and optical response to a stoichiometric trefoil-like reconstruction is strongly chalcogen-dependent and is governed by the interplay among local geometrical distortion, W 5d–chalcogen p hybridization, and spin–orbit coupling.

Crystals doi: 10.3390/cryst16090581

Authors: Hanhong Zhang Shaolong Chen Yushan Yang

Butylammonium acetate (BAAc) was investigated as a concentration-dependent precursor additive for inverted triple-cation perovskite solar cells based on FA0.80Cs0.07MA0.13PbI2.64Br0.39. BAAc loadings ranging from 0 to 7 mol% were systematically compared to determine how moderate and excessive additive concentrations influence film formation, defect behavior, and device operation. At 3 mol% BAAc, the mean equivalent-circle grain diameter increased from 0.508 to 0.719 μm, and the median increased from 0.495 to 0.688 μm, while cross-sectional SEM confirmed a comparable absorber thickness of 500 ± 20 nm across the series. The PbI2-to-perovskite diffraction peak height ratio decreased from 0.2691 to 0.0427, and the intensity-weighted photoluminescence lifetime increased from 230.2 to 350.0 ns. Light-intensity-dependent open-circuit voltage, impedance spectroscopy, thermal admittance spectroscopy, and space-charge-limited current measurements consistently indicated reduced trap-assisted recombination and transport loss at this concentration. In the EIS analysis, BAAc-3 showed the lowest transport resistance (222.17 ± 9.52 Ω) and the highest recombination resistance (8.211 ± 0.061 kΩ); all principal resistance parameters had relative standard errors below 10%, although systematic high-frequency residuals limit quantitative interpretation of the transport CPE. The champion BAAc-3 device reached 23.37% efficiency, compared with 20.42% for the control, and the 50-device mean increased from 19.63 ± 0.45% to 22.77 ± 0.30%. At 7 mol%, the morphological and electrical trends reversed and the champion efficiency decreased to 19.34%, which defines an over-treatment boundary. The 30-day dry–dark storage and 120 min maximum-power-point tests provide comparative, short-duration stability evidence. The concentration dependence is consistent with a literature-supported working model of precursor coordination and ammonium–halide interactions, without constituting direct spectroscopic identification of a specific complex.

Crystals doi: 10.3390/cryst16090579

Authors: Steluța Radu Ștefan Lucian Toma

This study evaluated the storage stability of tomato juice, paste, and purée packaged in conventional aluminium containers (ACs) and aluminium containers coated with a food-grade stainless steel layer (ASSCs). The objective was to determine whether the stainless steel coating could reduce aluminium ion migration, preserve the physicochemical and nutritional quality of tomato products during storage, and decrease the need for antioxidant, antifungal, and acidifying additives. The stainless steel coating improved the barrier performance of the Al substrate by reducing its porosity from 6.0% to 3.8%. During storage, tomato products in ACs exhibited a marked decrease in acidity (7.65–4.07 g/100 g), whereas samples stored in ASSCs showed a smaller reduction (7.65–5.98 g/100 g), indicating enhanced chemical stability. Increasing NaCl concentrations promoted Al migration, reaching 26.4 mg/kg in AC but only 9.2 mg/kg in ASSC. The vitamin C content remained nearly unchanged (2.09–2.04 mg/100 g), while total polyphenols decreased slightly (110.13–98.81 mg/100 g). Mineral analysis (Al, Cr, Mn, Ni, Zn, Fe, and Ca) confirmed higher metal concentrations in AC-stored samples, whereas aluminium migration was effectively minimised in ASSCs. These findings demonstrate that stainless steel-coated aluminium provides superior corrosion resistance, limits metal transfer, preserves the physicochemical and antioxidant quality of the tomato products, and represents a promising packaging material for extending shelf life while reducing the need for food additives.

Crystals doi: 10.3390/cryst16090578

Authors: Congzheng Ji Fengang Zheng

In this study, Se-excess Ge2Sb2SexTe1 (GSST) thin films were synthesized via magnetron co-sputtering. The crystal structure, surface morphology, complex refractive index, and bandgap of the Se-excess GSST thin films were systematically investigated. Owing to the formation of higher-energy Sb–Se bonds at an annealing temperature of 350 °C, grain refinement occurred (the average dendrite trunk width decreased from 0.64 μm to 0.37 μm). Consequently, the extinction coefficient (k) in the crystalline state was reduced to 0.17, resulting in a figure of merit (FOM) of 8.76 at the telecommunications C-band wavelength of 1550 nm.

Crystals doi: 10.3390/cryst16090577

Authors: Aumaparn Phlayrahan Nantharat Bunnag

This study investigated the effects of progressive step-heating (300–500 °C) and direct heating (500 °C) on pinkish-orange and red tourmalines using colorimetric, spectroscopic, and chemical analyses. Heating progressively modified visible absorption and color, with treatment at 500 °C generally increasing lightness (L*) and substantially decreasing chroma (C*), accompanied by weakening of the broad absorption near 520 nm while strong pleochroism was retained. Chemical analyses revealed substantial compositional variability, particularly in Mn and Fe, although elemental abundance alone did not account for the observed optical responses. Color evolution was associated with changes in overlapping electronic absorption features, but the underlying microscopic processes could not be uniquely assigned to specific transition-metal ions or oxidation-state changes. Fourier transform infrared (FTIR) spectroscopy showed preservation of the principal framework-related vibrational features up to 500 °C, with no evidence of major structural disruption. Within the present step-heating series, 400 °C produced an intermediate outcome characterized by measurable lightening and desaturation while retaining more of the original pink-to-red chromatic component than after treatment at 500 °C, which produced substantially greater desaturation.

Crystals doi: 10.3390/cryst16090576

Authors: Jisub Hwang Hackwon Do Jun Hyuck Lee

Class III aminotransferases represent a structurally and functionally unique subgroup. However, the contribution of specific loop elements to their active-site architecture and cofactor-dependent structural transitions remain underexplored. We elucidated the structural framework underlying the catalytic function of class III fold Pyridoxal 5′-phosphate-dependent aminotransferase from the Antarctic bacterium Hymenobacter sp. PAMC 26554 (HyAT), and report its crystal structure at 2.31 Å resolution. The structure revealed a canonical class III fold organized as a functional homotetramer. Structural analysis identified a proline-containing motif (P-x-P) within the α10-α11 loop, which induces intrinsic disorder at the active-site entrance in the apo-form and revealed that a cooperative disorder-to-order transition is requisite for active-site assembly upon cofactor binding. We propose that this flexible loop region may be involved in modulating substrate access. Notably, this proline motif was conserved in homologs from Hyperthermophiles, despite the cold-adapted nature of HyAT. This convergence implies a common evolutionary strategy where the geometric constraints of proline are exploited to decouple local active-site dynamics from global scaffold stability, thereby addressing the stability–activity trade-off across diverse thermal environments. Our findings provide new molecular insights into the structural dynamics of class III aminotransferases and highlight evolutionary strategies for tuning enzyme flexibility in extreme environments.

Crystals doi: 10.3390/cryst16090575

Authors: Andrés Aracena Kerry Wrighton-Araneda Katherine Pezet Diego Vilches Felipe A. Angel Ihan Chandía César Zúñiga Sebastián Elgueta Javiera González

A new nitro- and cyano-functionalized, tetradecyl-substituted benzothienoquinolizinium tetrafluoroborate was synthesized through oxidative photocyclisation of a pyridinium precursor and evaluated as a potential small molecule N-type organic semiconductor. The precursor and the photocyclised salts were characterized by UV–Vis absorption spectroscopy, DSC, 1H and 13C NMR, and cyclic voltammetry. Their optoelectronic properties were further investigated by DFT and TD-DFT calculations. Photocyclisation induced a marked bathochromic extension of the absorption profile, decreasing the optical band gap from 3.19 eV for the pyridinium precursor to 2.61 eV for the fused benzothienoquinolizinium salt. Cyclic voltammetry revealed a stabilized electrochemical LUMO level of approximately −3.87 eV, supporting the electron-deficient character of the nitro/cyano-substituted cationic scaffold. Frontier molecular orbital analysis showed that the HOMO and LUMO are mainly localized on the fused π-conjugated core and electron-withdrawing aryl substituents, with negligible contribution from the tetradecyl chain and BF4− counterion. TD-DFT and electron excitation analyses indicated that the monomeric low-energy transition has mixed local/charge-transfer character, whereas π-stacked dimers, especially the face-to-face arrangement, enhance charge transfer character and reduce electron–hole Coulombic attraction. Marcus type charge transport calculations revealed packing dependent behavior, with the face-to-face dimer displaying nearly ambipolar transport with a slight electron preference. A preliminary theoretical donor–acceptor model with hexaphenyl-substituted hexabenzocoronene further suggested energetic compatibility and strong intermolecular charge-transfer character. Overall, these results identify this benzothienoquinolizinium tetrafluoroborate as a promising electron-deficient cationic π-scaffold for future organic optoelectronic materials.

Crystals doi: 10.3390/cryst16090574

Authors: José Antonio García-Merino

Porous multi-walled carbon nanotube (MWCNT) films combine strong optical absorption with thermal, Kerr-like, thermo-optical, and magneto-optical responses. However, these effects depend on film structure and may require different design conditions. In this work, a multiphysics model was used to analyze 12 MWCNT film configurations with dependance on thicknesses, porosity, and orientation parameters. The model included optical attenuation, transient heating, nonlinear refraction, thermo-optic modulation, magneto-optical response, and optical phase shift under irradiances of 7–20 MW cm−2 and magnetic fields up to 1 T. Optical density ranged from approximately 0.4 to 2.8, while transmittance showed negligible variation with irradiance. Thin and porous films produced the highest temperature rises, approximately 4.5 K, and the largest total refractive-index changes. In contrast, thicker films generated larger accumulated phase shifts. The thermo-optic contribution is dominated under nanosecond laser irradiation. As the pulse duration approached the picosecond regime, the lower deposited energy reduced the photothermal response, so the Kerr-like and magneto-optical terms accounted for a larger total refractive-index change. This predictive parametric study identifies architecture- and pulse-dependent trends for future experimental evaluation of multifunctional MWCNT films.

Crystals doi: 10.3390/cryst16090573

Authors: Ming Zeng Jun Zhu Wei Zhang

This study leverages multiple machine learning algorithms for defect detection in friction stir welding (FSW), utilizing force-derived features as model inputs. Furthermore, the underlying relationships between welding forces and defect formation were systematically investigated, alongside an evaluation of the efficacy of force-feature-driven defect detection models. Results indicated that the variations in the averages and waveforms in the traverse force (Fx), lateral force (Fy) and plunge force (Fz) are highly responsible for the defect formation in FSW joints, such that an increase in Fy causes waveform distortions in Fx and Fy. Fyavg is the most important feature for the defect formation for 724 sets of experimental data. Defect detection based on thresholding of Fyavg and Fzavg achieves an accuracy of 80.3%. In contrast, four machine learning algorithms—Decision Tree (DT), K-Nearest Neighbors (KNNs), Support Vector Machine (SVM), and Artificial Neural Network (ANN)—were employed to construct defect detection models using the extracted force features as inputs, yielding accuracies of 93.5%, 97.5%, 95.7% and 94.9%, respectively. These findings further elucidate the underlying mechanics, that is, Fx and Fy primarily originated from the extrusion and shear forces induced by the probe’s rotation and traverse, whereas Fz was predominantly attributed to the compressive action of the shoulder.

Crystals doi: 10.3390/cryst16090572

Authors: Lin Yang Fuheng Nie Guijun Mao Jikun Yang Tieshan Cao Xingdong Chen Xiaopeng Zhang

This study investigates the high-temperature high-cycle-fatigue behavior of TIG-welded Haynes 230 alloy using smooth and notched specimens (Kt = 3) at 850–950 °C. Both elevated temperature and notch effect significantly degrade fatigue performance. As temperature increases, thermally activated crack initiation and propagation accelerate, shifting the S–N curves downward. Notched specimens exhibit substantially shorter fatigue lives due to stress concentration-induced multi-source crack initiation, dispersed propagation zones, and fragmented sudden fracture zones. The alloy shows low notch sensitivity across the test temperature range, with the lowest value at 900 °C. A unified fatigue life prediction model is established using a temperature correction factor exp[P × ()], demonstrating high fitting accuracy. M-G curves of notched specimens shift downward and leftward, revealing the aggravating effect of the notch on creep–fatigue interaction. Fractographic analysis shows that with increasing temperature, smooth specimens exhibit expanded sudden fracture zones and degraded striations, while notched specimens display multi-source initiation and a composite morphology of striations with fine dimples, consistent with macroscopic mechanical behavior. This work delivers comparative experimental data and mechanism-oriented insights for TIG-welded Haynes 230 joints within 850–950 °C; the proposed temperature-corrected model is valid for the investigated test window and provides reference for component performance analysis.

Crystals doi: 10.3390/cryst16090571

Authors: Robert T. Bondokov Shogen Matsumoto Connor G. Carr Kasey Hogan Griffin Q. Norbury Masato Kobayashi James Grandusky

Ultrawide bandgap (UWBG) semiconductors are destined to become the foundation for next-generation power and radio-frequency (RF) electronic devices. Their superior qualities such as high thermal conductivity, strong critical electric field, and robust mechanical and radiation hardness are driving continuous and widespread research. Amongst the UWBG materials, aluminum nitride (AlN) is highly attractive due to its direct ultrawide bandgap of about 6.2 eV, resulting in one of the highest Baliga’s and Johnson’s figures of merit. Equally important as its properties are material availability and growth methods capable of producing large-diameter substrates. In this work we report on bulk growth of 100 mm AlN crystals using the physical vapor transport (PVT) technique. The thermal gradients were simulated and tailored to obtain adequate thermal stresses, resulting in substrates with narrow X-ray rocking curves and dislocation densities in the range of 102–105 cm−2. In addition, the room-temperature thermal conductivity measured in two directions, perpendicular and parallel to the c-axis, was confirmed to be 300 W m−1 K−1. AlN substrates also demonstrated high UV transparency with absorption coefficients as low as 10 cm−1 at 265 nm wavelength. These results, along with the availability of 100 mm substrates, demonstrate that AlN is ready for further exploration and development for the power and RF electronics industry.

Crystals doi: 10.3390/cryst16090570

Authors: Anmin Li Xia He Zhuofang Huang Zhi Wang Yixin Yuan Yushi Gong Chunrong Chen

Nickel coatings were deposited onto the surfaces of red mud, Al2O3, and Fe2O3 particles via an electroless plating technique. The nickel-coated particles (1.5 wt.%) were subsequently incorporated into a ZL109 aluminum alloy matrix to fabricate three types of composites using a stir-casting process, followed by a T6 heat treatment consisting of solution treatment at 515 °C for 8 h, water-bath quenching at 90–100 °C, and artificial aging at 175 °C for 12 h. The microstructural morphology and phase identification were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Furthermore, the high-temperature tensile properties of the fabricated alloys were evaluated at 350 °C and 400 °C. The results showed that the addition of 1.5 wt.% nickel-coated red mud led to a more uniform distribution of eutectic silicon and an increase in the content of the Al5Cu2Mg8Si6, Al7Cu4Ni, and Al2Cu strengthening phases. These microstructural changes significantly enhanced the high-temperature tensile performance of the alloy. At 350 °C and 400 °C, the alloy reinforced with 1.5 wt.% nickel-coated red mud achieved tensile strengths of 97.8 MPa and 86.2 MPa, respectively. The combination of an appropriate amount of nickel-coated red mud and a suitable heat treatment process effectively improves the high-temperature stability and tensile properties of the ZL109 aluminum alloy, which could be attributed to the synergistic strengthening effect arising from the precipitation of high-temperature stable phases and the Orowan mechanism.

Crystals doi: 10.3390/cryst16090569

Authors: Meng Xiang Xianjun Shi Ruochen Sun

This study employs molecular dynamics (MD) simulations to explore the high-speed impact behavior of double conical tungsten (W) fragments on titanium (Ti) target plates, focusing on fragment cloud formation, Ti damage evolution, and the effects of temperature and impact velocity. High-speed impact converts W fragments’ kinetic energy into internal energy, causing W fragmentation and the formation of a mixed-phase fragment cloud, which induces severe damage to the Ti target. Under double-particle impacts, W fragments penetrate the Ti target to form a multi-source fragment cloud, with Ti target damage (characterized by amorphous phase distribution) undergoing initiation and extension stages. Higher temperatures broaden the high-temperature damage zone and increase crater size but do not change the impact penetration evolution mode or penetration depth. Impact velocity determines damage modes: low velocity causes non-through internal damage with a rear bulge, while high velocity leads to full perforation with mixed W-Ti fragment ejection, and lateral crater size is almost unaffected by velocity. This study innovatively reveals the atomic-scale damage evolution mechanism of Ti targets under dual conical W fragment impact, which fills the research gap in conventional single-fragment impact studies. These findings clarify the high-speed impact mechanism of Ti alloys, providing theoretical support for the design of Ti-based protective structures in engineering.

Crystals doi: 10.3390/cryst16090568

Authors: Na Yeong Ko

This study investigates the effect of initial microstructure on the high-pressure mechanical properties of high-purity tin (Sn). Two Sn samples from the same commercial product were measured using high-pressure X-ray diffraction in diamond anvil cells. At ambient pressure, the two samples exhibited different initial crystallographic orientations; one showed random orientation, while the other exhibited preferred orientation (i.e., texture). In the low-pressure β-Sn phase, both samples exhibited the same bulk moduli with B0 = 55.0 ± 0.4 and 55.0 ± 2.3 GPa, respectively. However, their compressional behavior diverged significantly after the phase transition from β-Sn to the body-centered tetragonal (BCT) phase. The measured bulk moduli for the BCT phase were 60.0 ± 0.9 GPa for the randomly oriented Sn and 91.3 ± 1.4 GPa for the textured one. These results indicate that the initial microstructure can significantly influence the compressional response of Sn under high pressure.

Crystals doi: 10.3390/cryst16090567

Authors: Ziyuan Xu Fu Xiao Yuanbiao Tan

D406A steel serves as a critical structural material for load-bearing components in aerospace solid rocket motors. To achieve an excellent strength-plasticity balance of D406A steel in this work, the quenched specimens austenitized at 890 °C were subjected to tempering treatments at 320 °C, 350 °C, 380 °C and 410 °C, respectively. SEM and EBSD characterization were adopted to systematically investigate the effects of tempering temperature on the microstructure, grain boundary characteristics, local strain, Schmid factor and mechanical properties. The results reveal that the lath martensite gradually undergoes recovery and disintegration with increasing tempering temperature, while the fraction of low-angle grain boundaries rises first and then falls, reaching the maximum value of 48.2% for the specimen tempered at 350 °C. At this tempering temperature, the KAM distribution is uniform, the Schmid factors shift toward the medium-to-high range, the proportion of grains with soft orientation increases, and the deformation coordination capacity is optimal. The specimen tempered at 350 °C exhibits an ultimate tensile strength of 1633.9 MPa, a yield strength of 1262.5 MPa and a Vickers hardness of 485.4 HV, achieving the optimal synergy between strength and plasticity.

Crystals doi: 10.3390/cryst16090566

Authors: Tong-Hui Yao Wenqiang Sun

Recent research has shown that Cu atoms can incorporate into the L12−Al3Sc precipitates in Al-Cu-Sc alloys, forming Al3−xCuxSc compounds that serve as effective hydrogen traps. Nevertheless, the Cu-induced modifications to the stability and mechanical properties of these precipitates have not yet been systematically quantified. In this work, first-principles calculations are performed to systematically investigate the crystal structures, phase stability, elastic properties, and thermodynamic behavior of Al3−xCuxSc (x = 0, 1, 2, 3) compounds. Structural optimizations are carried out for all compositions, and the formation enthalpies, elastic constants, polycrystalline moduli, and Debye temperatures are derived from the computed total energies and stress–strain relationships. The calculations reveal that Al2CuSc and AlCu2Sc adopt tetragonal structures rather than the cubic L12-type symmetry found in Al3Sc and Cu3Sc, indicating a composition-driven structural transition. The formation enthalpy becomes progressively less negative with increasing Cu content, implying a reduction in thermodynamic driving force for compound formation. The computed elastic properties further show that Cu substitution decreases the bulk-to-shear modulus ratio and the Vickers hardness, while simultaneously enhancing the ductility of the material. Additionally, the Debye temperature exhibits a monotonic and rapid decrease from Al3Sc to Cu3Sc, reflecting a significant softening of the lattice vibrational spectra upon Cu alloying. These quantitative theoretical results provide a comprehensive basis for understanding the compositional dependence of the mechanical and thermal responses of Cu-modified Al3Sc precipitates.

Crystals doi: 10.3390/cryst16090565

Authors: Natsumi Yano Ko Ikeda Makoto Handa Yusuke Kataoka

A cyclometalated iridium(III) complex [Ir(ppy)2(tpdp)]PF6 ([1]PF6; ppy = 2-phenylpyridinate, tpdp = 5,6,7,8-tetraphenyl-1,12-diazatripheneylene) was synthesized and structurally characterized by single-crystal X-ray diffraction analysis. In [1]+, two nitrogen atoms of tpdp coordinate to the iridium(III) ion with Ir-N distances of 2.131(4) and 2.114(4) Å. The peripheral phenyl substituents of tpdp are oriented nearly perpendicular to the enlarged π-conjugated plane of tpdp. [1]PF6 exhibits shoulder bands at 472, 407, 368, and 337 nm, while the absorption increases continuously from ca. 520 nm toward shorter wavelengths. This spectral feature is similar to that of [Ir(ppy)2(phen)]PF6 ([2]PF6), but the absorption intensity is much higher for [1]PF6 in the UV region. The contribution from the π–π* transition of the tpdp ligand was considered to be the reason that [1]PF6 exhibits such strong absorption in the UV region. Furthermore, [1]PF6 exhibits an emission from 3MLLCT at 558 nm, whereas [2]PF6 exhibits it at 560 nm. The luminescence lifetime (τ) of [1]PF6 was 411 ns, shorter than that of [2]PF6 (900 ns), and the absolute quantum yield (Φ) of [1]PF6 was 4.8%, lower than that of [2]PF6 (20.5%). Cyclic voltammetry (CV) analysis in degassed CH3CN revealed redox waves both at the negative and positive sides (E1/2 = 1.28 and −1.38 V vs. SCE) for [1]PF6. In addition, DFT calculations were performed to discuss the electronic structures and photophysical properties of [1]+.

Crystals doi: 10.3390/cryst16090564

Authors: Zhongqi Chen Minghui Li Liya Zhao Yuqi Zhang Jiazuo Meng Hongxing Wu Haoni Ma Hui Zhang Guili Zheng

With continuing advances in interfacial sensing and tunable micro-optics, the potential applications of hemispherical nematic droplets in these fields have received increasing attention. Local variations in surface anchoring can modify their director configurations and thereby produce distinct optical responses. However, the specific manner in which anchoring conditions govern director configurations and defect formation remains poorly understood. Using the Landau–de Gennes theory, we investigate a model of a hemispherical droplet bounded by a curved surface and a planar base, with homeotropic easy-axis orientations prescribed at both interfaces. Four anchoring scenarios are compared: uniform anchoring, continuously varying curved-surface anchoring, localized weak-anchoring bands placed at different positions, and combinations of curved-surface and planar-base anchoring strengths. The results show that droplet size, spherical-cap height, and the strength and spatial position of anchoring all affect the director defect formation. Reducing the curved-surface anchoring strength near the contact line allows the director field to vary more continuously in this region, thereby suppressing the formation of the ring-shaped defect-core region. Distinct configurations, including a split-core structure near the symmetry axis, are obtained when the planar-base anchoring strength is varied under strong curved-surface anchoring.

Crystals doi: 10.3390/cryst16090563

Authors: Nadezhda A. Zhuk Maria G. Krzhizhanovskaya Alexandra V. Koroleva Shamil S. Shayakhmedov Nikolay A. Sekushin Vladimir A. Belyy Olga V. Petrova Sergey V. Nekipelov Ratibor G. Chumakov

The article presents the results of a study of the properties of a new pyrochlore (Bi2.7Mg0.46Ni0.70Sb2O10+Δ) using X-ray powder diffraction analysis, high-temperature X-ray powder diffraction and thermal analysis, diffuse reflectance spectroscopy, impedance spectroscopy, and X-ray spectroscopy methods (XPS, NEXAFS). The Ni/Mg codoped bismuth stibate pyrochlore was synthesized using the solid-phase method. The best results of the Rietveld structure refinement were achieved for the disordered pyrochlore model (sp. gr. Fd-3m:2, a = 10.47574(6) Å). The results of modeling the cation distribution over crystallographic positions are presented. The thermal expansion coefficient (TEC) of pyrochlore increases monotonically from 6.8 × 10−6 °C−1 (30 °C) to 9.8 × 10−6 °C−1 (810 °C). Above 1080 °C, thermal dissociation of pyrochlore occurs with the formation of (Mg/Ni)Sb2O6 and two cubic phases. At temperatures below 200 °C, the sample exhibits primarily capacitive impedance. The sample capacitance (~17 pF) is independent of temperature and frequency up to 200 °C. The high-frequency relative permittivity and dielectric loss tangent are 30.5 and 5 × 10−4 (24 °C, 5 × 104 Hz). The activation energy for conductivity is 0.99 eV. The analysis of NEXAFS and XPS spectra allowed for the determination of the charge state of the metal cations: Bi + (3-δ), Sb + (5-δ), Ni/Mg + 2.

Crystals doi: 10.3390/cryst16090562

Authors: Natalina Makieieva Teobald Kupka Krzysztof Ejsmont

Cathinone and its synthetic derivatives are one of the most commonly used narcotics in the world. Some studies describe their antidepressant and smoking cessation potential, as well as cytostatic activity on several cancer cell lines. The literature presents a limited amount of data on the polymorphism in cathinones crystals, as well as on the correlation between aromaticity and crystal stability. This work aims to analyze the effect of the crystal structure on the nucleus-independent chemical shift (NICS) and the harmonic oscillator model of aromaticity (HOMA) values of bk-2C-B cathinone derivative polymorphs—EBIJOR and EBIJUX. A comparative analysis of NICS and HOMA values with an isolated drug molecules is also performed in this study. A higher aromaticity of molecules in polymorph EBIJOR was observed, compared to in EBIJUX. This may indicate a higher stability of EBIJOR compared to EBIJUX.

Crystals doi: 10.3390/cryst16090561

Authors: Dongxiao Hong Manyu Hua Li Wang Xixi Ji Pengfei Wu Jian Liu Binggong Yan Zhihai Cai Yejun Li Yonggang Tong

In order to enhance the strength and wear resistance of pure copper without obvious sacrifice of high electrical conductivity, Al2O3 particle-reinforced copper matrix composites with different volume fractions of Al2O3 were fabricated via the oscillatory hot-pressing sintering process. The effects of Al2O3 content on the densification, microstructure, mechanical properties, electrical conductivity, and wear behaviors of the composites were systematically investigated. The results showed that oscillatory pressure effectively inhibited pore formation, and Al2O3 particles were uniformly distributed within the copper matrix. With the increase in the Al2O3 volume fraction, the densification of the composites decreased slightly, while the hardness, compressive strength and wear resistance were continuously improved. By contrast, the electrical conductivity declined marginally and the friction coefficient rose. The 10 vol.% Cu-Al2O3 composite exhibited the optimal comprehensive wear resistance, with a hardness of 123 HV and an electrical conductivity maintained at 80.2% IACS. The wear mode of the composites gradually shifts from single adhesive wear of pure copper to the combined effect of abrasive wear and oxidative wear.

Crystals doi: 10.3390/cryst16090560

Authors: Aya Emad Alhussaini Mohammed Dheyaa Saad Mohanad Adil Hussein Mohammad Javad Maleki Mohammad Soroosh

In this work, a novel all-optical 4-to-2 encoder employing nonlinear resonant cavities in a two-dimensional photonic crystal is proposed and numerically investigated. The encoder consists of a lattice of chalcogenide rods incorporating nonlinear Kerr-effect cavities, enabling selective wavelength coupling through intensity-controlled resonance. By assigning three distinct optical input power levels, the proposed architecture successfully realizes all encoding states without requiring additional control signals or complex resonator configurations. Numerical results demonstrate correct encoding functionality with normalized logic-1 output powers ranging from 0.89 to 1.71 and logic-0 levels below 0.013, yielding a high contrast ratio of 18.35 dB. The encoder exhibits ultrafast temporal performance with a maximum rise time of only 108 fs, corresponding to a data transmission capability of 4.63 Tbit/s, while maintaining a low insertion loss of 3.73 dB. Furthermore, the proposed structure occupies an ultra-compact footprint of only 95 μm2, outperforming previously reported photonic crystal encoders in terms of integration density and speed. With regard to its compactness, high switching speed, excellent signal discrimination, and compatibility with current nanofabrication technologies, the proposed encoder represents a promising building block for future photonic integrated circuits, optical computing systems, and high-capacity optical communication networks.

Crystals doi: 10.3390/cryst16090559

Authors: Baicheng Liu Hongliang Zhang Shenghan Li Yurii Luhovskyi Zhisheng Nong

Aluminum alloy is a lightweight, high-strength material based on aluminum matrix with the addition of elements such as copper, magnesium, silicon, zinc, manganese, or lithium. Featuring low density, high specific strength, excellent formability, and outstanding corrosion resistance, it is widely applied in the fields of aerospace, rail transit, automotive lightweighting, and additive manufacturing. In the aerospace sector, fatigue failure constitutes the primary failure mode of load-bearing components. This paper reviews the influence mechanisms of various strengthening technologies, namely shot peening (SP), laser shock processing (LSP), physical vapor deposition (PVD), micro-arc oxidation (MAO), anodic oxidation (ANO), additive manufacturing, casting, extrusion, and heat treatment, on the fatigue properties of aluminum alloys; analyzes the regulatory effects of process principles, coating compositions, and microstructures (grains, phase composition, and interfacial bonding) on crack initiation and propagation; discusses the synergistic effect between plastic deformation strengthening and coating functionality; summarizes the key material and process factors affecting the fatigue life of aluminum alloys; and finally prospects the technical development trends driven by high-reliability service requirements.

Crystals doi: 10.3390/cryst16090558

Authors: Xingyou Gao

The edge-defined film-fed growth (EFG) method is the dominant industrial technique for producing large-area β-Ga2O3 single-crystal substrates, but thermal stress-induced dislocation generation remains a critical barrier. This work presents a coupled thermo-mechanical finite-element framework for thermal-stress management in EFG-grown β-Ga2O3. The central methodological contribution is a 500-sample gradient-boosting surrogate sensitivity analysis (R2=0.955, mean absolute error (MAE) =11.3 MPa) that quantitatively decomposes thermal-stress variance into controllable process factors and irreducible material-property uncertainties. The physical foundation comprises two enabling elements: (i) the full 21-component monoclinic Voigt stiffness matrix with explicit crystal–model coordinate mapping, for which the orthotropic model is rigorously shown to be exact in 2D plane strain through an exact kinematic theorem showing that the 2D plane-strain results of prior orthotropic EFG analyses are unaffected by the coupling terms, while the monoclinic formulation provides the essential foundation for future 3D studies; and (ii) a dimensionless and numerical justification for omitting melt convection, which enables 100% solver convergence (500/500 Latin hypercube samples) with stress errors < 1.5 MPa. Afterheater temperature TAH is the leading controllable parameter (35.9%), nearly tied with the elastic constant C33 (35.5%), followed by the thermal-expansion component αc (15.9%). Elevating TAH from 1900 K to 1950 K reduces the peak von Mises stress by ∼29% (COMSOL Multiphysics 6.2-verified); the 2D plane-strain baseline anchors the surrogate analysis at σmax=223 MPa, while the afterheater-free 3D configuration gives σmax=187 MPa at the crystal periphery near the solid–liquid interface. The isotropic approximation underestimates peak stress by 39.6%, confirming that directional anisotropy is essential for quantitatively reliable thermal stress prediction in monoclinic oxide crystals.

Crystals doi: 10.3390/cryst16090557

Authors: Bijie Peng Mingyue He Ning Wang Jingyi Xu

Pakistan is recognized as a notable source of gem-quality peridot, which is renowned internationally for its attractive yellowish-green to light greenish-yellow color and large crystal size. This paper elucidates the petrogenesis of Pakistani peridot based on coupled gemological, mineralogical, and geochemical evidence. Pakistani peridot is commonly associated with serpentine, magnetite, and minor talc, occurring within pockets and veins of serpentinized dunite. The most common inclusions identified in peridot include ludwigite, magnetite, serpentine, and brucite. Among these, ludwigite inclusions serve as a significant indicator for geographic origin determination. Pakistani peridot exhibits significant internal compositional heterogeneity, with forsterite (Fo) contents ranging from 88 to 96. Trace element analyses show that Pakistani peridot is enriched in incompatible elements such as boron and lithium. The peridot samples yield δ18O compositions spanning 3.94‰–6.17‰, averaging 5.04 ± 0.63‰. Isotopic signature confirms a mantle-derived signature and precludes significant involvement of crustal-derived fluids. The mineral composition and geochemical characteristics, combined with the geological setting, suggest that the Pakistani gem-quality peridot precipitated from B- and CO2-rich subduction-derived hydrothermal fluids, which migrated along extensional fractures within the highly permeable dunites.

Crystals doi: 10.3390/cryst16090556

Authors: Abílio M. P. de Jesus

Fatigue and fracture continue to represent some of the most important degradation and failure mechanisms affecting engineering structures and components [...]

Crystals doi: 10.3390/cryst16090555

Authors: Hrudya Pariyacheri Padikkal Olivier Jeannin Nicolas Quéméré Ie-Rang Jeon Marc Fourmigué

Cyclic 1,2-diselenides are known to exhibit three σ-holes around the Se atoms—two in the prolongation of the Se–Se bond and one merging the two electron-depleted areas in the prolongation of the C–Se bonds. Among them, naphthalene peri-diselenides were recently isolated in their radical cation form with halometallates, affording 1:1 salts, where charge activation upon oxidation leads to strong Se•••Cl/Br chalcogen bond (ChB) interactions. Acenaphthene peri-diselenide (1) is shown here to be readily oxidized to its cation radical, showing various association modes of the 1+• species in the solid state. When engaged in electrocrystallization experiments with (Bu4N)(FeCl4), acenaphthene peri-diselenide (1) afforded two salts of the radical cation, formulated as (1)2(Fe2Cl6O) and (1)(FeCl4), depending on the electrocrystallization conditions. In both salts, short and highly directional Se•••Cl chalcogen bond (ChB) interactions take place, simultaneously involving all three σ-holes surrounding the diselenide bridge, with the reduction ratio (relative to the van der Waals Se•••Cl contact distance of 1.90 + 1.75 = 3.65 Å) reduced to 0.89. In addition, while cation radicals in (1)2(Fe2Cl6O) adopt head-to-tail alternated stacks without any intermolecular Se•••Se contacts, they organize in (1)FeCl4 into twisted-cofacial dimers, with an intra-dimer Se•••Se contact as short as 3.197(2) Å, i.e., a reduction ratio of 0.84. Such structural organization is reminiscent of those observed in dithiadiazolyl/diselenadiazolyl radicals, which associate into dimers, most often in a cis-cofacial geometry. Here, the 1+• radicals adopt either a head-to-tail (trans-cofacial) geometry (in the Fe2Cl6O2− salt) or a distorted twisted-cofacial geometry (in the FeCl4− salt), further stabilized by the chelating FeCl4−.

Crystals doi: 10.3390/cryst16090554

Authors: Zhijun Wang

The precise characterization of micro-strain distribution within crystalline materials using Laue crystallography methodology is critically important. Applying the strain tensor based on the Green–Lagrange deformation matrix to represent the hkl lattice strain tensor often suffers from insufficient accuracy and drawbacks in evaluation criteria, especially for non-cubic crystal systems. To address these challenges, a novel algorithm hklstrain is designed. The unstrained interplanar spacing d0 is obtained according to the theoretically indexed spot positions, while the strained interplanar spacing dmes is obtained via the global fitting method according to the principle of Laue X-ray reflection and orientation information, and then the micro-strain of all lattice planes of interest is mapped into the sample coordinate system. hklstrain reaches a strain resolution down to 2 × 10−4, and quantitatively determines the orientation-dependent micro-strain fields, offering intuitive insights into the characterization of crystalline materials. It has been successfully applied in the BL03HB beamline at Shanghai Synchrotron Radiation Facility (SSRF) for micro-strain analysis. In contrast to Green–Lagrange strain tensor method, hklstrain produces reliable orientation-dependent micro-strain maps of interplanar spacing variation, thus providing significant advantages in strain tensor analysis for crystalline materials using Laue crystallography methodology.

Crystals doi: 10.3390/cryst16090553

Authors: Shanquan Deng Junwei Zhu Meihua Bian Xingseng Zhang Heng Chen Yuyin He Jianing Peng

The effects of equimolar La/Ce co-doping (0–0.4 wt.% of each element) on the microstructure, mechanical properties, and electrical conductivity of the Al-0.5Fe (8176) conductor alloy were investigated in the as-cast, cold-drawn, and annealed (300 °C, 2 h) states. La/Ce additions refine the as-cast eutectic cells and modify the detrimental Al13Fe4 intermetallic from coarse plate-like to fine spheroidal particles. At 0.3 wt.% La + 0.3 wt.% Ce (0.3LC), the annealed wire reaches a peak elongation of 16.7% (+42.7% relative to the rare-earth-free alloy), while its electrical conductivity rises from 59.87 to 61.81% IACS. The conductivity increase is explained by a solute-scavenging mechanism: La and Ce bind Fe and Si impurities into stable Al-RE intermetallics, reducing solute-induced electron scattering in the α-Al matrix. At the same time, thermally stable Al-RE dispersoids pin subgrain boundaries during annealing, retard recrystallization, and preserve the fine-grained structure that benefits ductility. Both effects originate from the same RE addition. This coupled scavenging–pinning pathway breaks the usual trade-off between conductivity and ductility and defines an optimal composition range for high-performance Al-Fe conductor alloys.

Crystals doi: 10.3390/cryst16090552

Authors: Fahed Alrshoudi Hossein Mohammadhosseini Rayed Alyousef Mahmood Md. Tahir Hisham Alabduljabbar Abdeliazim Mustafa Mohamed

The journal retracts the article titled “The Impact Resistance and Deformation Performance of Novel Pre-Packed Aggregate Concrete Reinforced with Waste Polypropylene Fibres” [...]

Crystals doi: 10.3390/cryst16090551

Authors: Omaima Guesmi Marwa Ben Arbia Faouzi Saidi Mohamed Ben Rabeh Abdelaziz Rabehi Mustapha Habib Elisabetta Comini Hassen Maaref

In this work, Cu2CoSnS4 (CCTS) thin films were deposited on glass substrates by thermal evaporation and investigated for photovoltaic applications. The influence of substrate temperature, varied from 25 °C to 200 °C, on the structural, morphological, and optical properties of the films was experimentally studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) measurements. XRD analysis confirmed the formation of crystalline CCTS with a stannite structure and a preferential orientation along the (112) plane. SEM observations revealed rough and non-uniform surfaces accompanied by an increase in grain size with increasing substrate temperature. Room-temperature PL measurements indicated a band-gap energy of approximately 1.3 eV, suitable for photovoltaic applications, and confirmed the presence of secondary phases in the p-type stannite CCTS films. Despite the promising photovoltaic properties of CCTS, numerical studies on CCTS-based solar cells remain scarce in the literature. In this context, a numerical study of the CCTS-based solar structure grown on glass was also performed using SCAPS-1D, showing good agreement with experimental photovoltaic results and validating the simulation model. Replacing the glass substrate with silicon improved the device efficiency to 5.77%. Further optimization of the series and shunt resistances significantly enhanced the photovoltaic performance, achieving a power conversion efficiency of 16.77%, with FF = 52.94%, Voc = 0.89 V and Jsc = 35.19 mA/cm2.

Crystals doi: 10.3390/cryst16090550

Authors: Ali Sincar Ethem Furkan Hıdır Cevher Kürşat Macit Samet Tekin Ukbe Usame Uçar Fatih Osmanlıoğlu

Heat-polymerized poly(methyl methacrylate) (PMMA) is widely used for denture bases but remains susceptible to surface deformation and sliding wear. This study evaluated the structure, chemistry, surface morphology, microhardness, and dry-sliding tribology of PMMA reinforced with 1, 3, and 5 wt.% cubic boron nitride (c-BN). Disk specimens (10 mm diameter × 2 mm thickness) were prepared; ten specimens per group were tested for Vickers microhardness and wear/coefficient of friction, while one representative specimen per group was examined by XRD, ATR-FTIR, and SEM/EDS before and after wear. The PMMA amorphous/semi-amorphous response and characteristic ester bands were retained, whereas c-BN-related diffraction features and B/N signals became more evident with reinforcement. Microhardness increased from 20.00 ± 0.70 to 45.00 ± 1.61 HV0.03. After 1000 m at 10 N and 1 m s−1, mass loss decreased from 32.4 to 9.8 mg and the overall coefficient of friction from 0.58 to 0.28. Post-wear SEM/EDS showed reduced grooving, smearing, and material detachment at higher c-BN contents. Statistical analysis confirmed large composition effects, and composition-window models reproduced the measured hardness and wear trends. Within the tested range, 5 wt.% c-BN provided the strongest surface-hardening and wear-suppression response under controlled dry-sliding conditions.

Crystals doi: 10.3390/cryst16080549

Authors: Adriana-Gabriela Schiopu Mihai Oproescu

The increasing demand for sustainable and environmentally synthesis routes has driven significant interest in biogenic precursors for nanomaterial fabrication. Among these, egg-derived materials—including eggshell, eggshell membrane (ESM), egg white, and egg yolk—have emerged as versatile, low-cost, and multifunctional resources for green nanotechnology. This review provides a comprehensive and critical analysis of the physicochemical properties and functional roles of egg-derived components in nanomaterial synthesis. A comparative evaluation of egg-derived and conventional synthesis methods is presented, highlighting the trade-off between environmental sustainability and control over physicochemical parameters. Egg-derived approaches offer reduced toxicity, lower energy consumption, and intrinsic functionalization, but remain limited by compositional variability, reduced reproducibility, and challenges in process scalability. Furthermore, an application-oriented framework is proposed for selecting appropriate egg-derived precursors based on material type, targeted functionality, and processing constraints. The review also identifies key limitations, including mechanistic uncertainties, organic residue formation, and regulatory considerations, and outlines future research directions focused on process standardization, in situ characterization, and hybrid synthesis strategies.

Crystals doi: 10.3390/cryst16080548

Authors: Najat A. Al Riyami John Husband Nawal K. Al-Rasbi

A new class of Ln(III) Schiff base (SB) complexes has been synthesized with the general formula [LnL(hfac)3], where Ln = Tb (TbL), Eu (EuL), Sm (SmL) or Gd (GdL). The molecular structure of the complex was determined using the X-ray diffraction method. The IR spectra show that the C=O stretching is shifted from 1695 cm−1 in pure PMMA to 1719–1724 cm−1 in LnL-PMMA hybrid materials. This means that LnL materials are successfully embedded into the PMMA backbone in the polymeric films. However, the Ln(III) SB complexes exhibit emission spectra that cover the visible region. The TbL complex displays an intense green emission combined with a large emission lifetime of 0.505 ms. However, the incorporation of Ln-SB complexes into PMMA (polymethylmethacrylate) polymeric films was investigated. The thermal stabilities of the LnL-PMMA hybrid materials increased from 140 to 250 °C when compared with the LnL-SB complexes. Furthermore, their luminescence intensity and lifetimes were also enhanced due to their induced structural rigidity. The molecular interactions of the LnL complexes with the PMMA matrix were monitored by investigating the luminescence properties of EuL-PMMA. Detailed photoluminescence studies showed insights into the non-radiative rates and improved quantum yields (QEu = 23%) from Eu(III). Furthermore, the higher values of Judd–Ofelt parameters Ω2 and Ω4 indicate strong hydrogen bonding interactions between L and PMMA. Nevertheless, these significant optical properties enable LnL-PMMA polymeric materials as colored phosphors for the design of opto-electronic devices.

Crystals doi: 10.3390/cryst16080547

Authors: Maksims Surovovs Stanislavs Luka Strozevs Janis Virbulis

The present study demonstrates the use of a transient multiphase flow model for the description of feed rod melting dynamics during the floating-zone silicon crystal growth process on a local scale. The presented numerical model is verified using a previously introduced analytical model of the thin melt layer on the open melting front. An artificial increase in viscosity on the liquid–gas boundary is used to minimize numerical effects, and good agreement with the analytical model is achieved in the system parameter range that describes a typical growth process. Simulations with a precise interface shape show that a stable solution is achieved in cases with different initial melt distributions, showcasing the re-establishment of melt flow after the thin melt layer breaks. The influence of flow rate fluctuations is investigated, and the obtained stable solution is maintained in the majority of the considered cases.

Crystals doi: 10.3390/cryst16080546

Authors: Ivan Erick Castañeda-Robles Abraham Leonel López-León Elí Rafael Pérez-Ruíz Javier Olguin-Coca Luis Daimir López-León

Corrosion of reinforcing steel remains a major cause of premature deterioration in concrete infrastructure, motivating the development of inhibitors with lower toxicity and reduced environmental impact. This review critically examines recent advances in green and bio-based corrosion inhibitors for reinforced concrete, including plant extracts, agro-industrial residues, naturally occurring organic compounds, proteins, polysaccharides, bio-based coatings, hybrid formulations, and microbial systems. The available evidence is synthesized in terms of chemical functionality, delivery route, adsorption and film-forming mechanisms, electrochemical response, compatibility with cementitious materials, and durability under chloride- and carbonation-related exposure. Many formulations provide substantial inhibition under optimized laboratory conditions through interfacial adsorption, coordination with iron species, passive-film stabilization, suppression of anodic and cathodic reactions, and restriction of aggressive-species transport. However, reported efficiencies are not directly comparable because experimental scale, exposure conditions, dosage, steel preparation, and calculation methods vary considerably. Moreover, long-term reinforced-concrete and field studies remain scarce, while extract standardization, cement compatibility, toxicity, biodegradability, and life-cycle performance are frequently insufficiently addressed. Green and bio-based inhibitors therefore represent a promising but heterogeneous technology class. Their practical implementation requires chemically reproducible formulations, complementary electrochemical and surface evidence, concrete-scale durability assessment, environmental validation, and stage-gated progression toward monitored field applications.

Crystals doi: 10.3390/cryst16080545

Authors: Mahmoud Fathy H. M. Hashem Medhat Ammar Mohamed Okil Ahmed Shaker Michael Gad A. E. Hassanien

The increasing demand for high-efficiency photovoltaic technologies has intensified research into tandem solar cells (TSCs) as a promising strategy to surpass the performance limits of single-junction devices. In this study, a comprehensive optoelectronic simulation using a Silvaco ATLAS TCAD simulator is employed to design, optimize, and compare two tandem architectures: all-organic and hybrid organic/silicon TSCs. The all-organic configuration consists of polymer donors comprising a PBDB-T:F-M top sub-cell stacked with a PTB7-Th:COi8DFIC:PC71BM bottom sub-cell, while the hybrid configuration integrates a PBDB-T:F-M organic top cell with a crystalline Si bottom cell. Calibrated device models, validated against experimental data of the individual sub-cells, are used to evaluate tandem performance and guide systematic optimization. The two tandem architectures employ the same PBDB-T:F-M wide-bandgap organic top absorber (Eg~1.60 eV), while the rear sub-cell consists of either the PTB7-Th:COi8DFIC:PC71BM organic absorber (Eg~1.20 eV) or crystalline silicon (Eg~1.12 eV). The initial organic/organic tandem device accomplishes a power conversion efficiency (PCE) of 15.70% and JSC of 10.96 mA/cm2, whereas the organic/silicon tandem structure exhibits a higher initial PCE of 16.85% and JSC of 12.26 mA/cm2. Following absorber-thickness optimization, the all-organic and hybrid OSC/Si tandems achieve PCEs of 19.44% and 21.13%, respectively. Rather than constituting a simple efficiency ranking, the comparison reveals distinct optical, electrical, and technological trade-offs. The hybrid architecture benefits from the broader spectral utilization and efficient carrier collection of thin crystalline Si, whereas the all-organic configuration offers advantages associated with low-temperature solution processing, reduced material consumption, and potentially fully solution-processed photovoltaic fabrication. The calibrated comparative framework therefore provides design guidance for selecting and optimizing TSCs according to both performance and application requirements.

Crystals doi: 10.3390/cryst16080544

Authors: Huaizhang Gu Haifeng Yin Yan Lei Run Zhao Wen Yang Ranyin Fu

The dissociative adsorption of O2 strongly depends on the activity of CO oxidation electrocatalysts. Using first-principles calculations, we investigated O2 dissociative adsorption on Cu-, Pt-, and Pd-doped Ag(111) surfaces. Our results show that the adsorption configuration designated t-b-t1 is the most energetically favorable adsorption state, with the O2 binding strength following the order AgCu(111) > AgPt(111) > AgPd(111) > Ag(111). By analyzing the factors that influence the d-band center, we infer that the ligand effect constitutes the dominant determinant of adsorption behaviour. For the subsequent dissociation of O2, our calculations identify a viable reaction pathway that begins with the t-b-t1 configuration and evolves into two oxygen adatoms adsorbed at adjacent hollow fcc sites. The computed energy barriers for this pathway follow the order Ag(111) > AgPt(111) > AgPd(111) > AgCu(111). These theoretical findings provide crucial guidance for the practical implementation of Ag-based bimetallic alloys as efficient CO oxidation electrocatalysts.

Crystals doi: 10.3390/cryst16080543

Authors: Ulises González-Vázquez Lizeth Rojas-Blanco Marcela del Carmen Arellano-Cortaza Ildefonso Zamudio-Torres Erika Viviana Miranda-Mandujano Rubén Alejandro Vázquez-Sánchez Erik Ramirez-Morales

Environmental pollution, particularly water contamination, requires the continuous development of robust, effective monitoring technologies. While chemical optical sensors offer significant advantages for environmental monitoring, many traditional devices rely on complex combinations of chemical dyes with specific acid dissociation constants. To overcome these limitations, this study presents a dye-free approach centered on a fiber-optic pH sensor based on a TiO2 thin film. The protective coating of multimode optical fibers was successfully removed using a controlled hydrofluoric acid (HF) treatment, enabling deposition of TiO2 films via a low-cost sol–gel dip-coating method. Structural characterizations through X-ray diffraction (XRD) and Raman spectroscopy confirmed the preferential growth and high purity of the anatase phase. Furthermore, energy-dispersive X-ray spectroscopy (EDS) confirmed the presence and relatively uniform distribution of Ti on the fiber surface. The optical performance of the sensor was evaluated using a 940 nm light source over a broad pH range (4–14), where the device exhibited distinguishable stepped optical-power responses at four pH conditions spanning pH 4–14. A preliminary analysis yielded an apparent average slope of 0.40 µW/pH. These results support the feasibility of using sol–gel derived TiO2 coatings in the preliminary development of dye-free optical devices for aqueous pH monitoring.

Crystals doi: 10.3390/cryst16080542

Authors: Ilona Zamaraite Andrius Dziaugys Juras Banys

Two-dimensional (2D) layered materials—graphene, hexagonal boron nitride (hBN), transition metal dichalcogenides (TMDs), and layered van der Waals (vdW) thiophosphates—constitute a rapidly expanding family whose properties are governed by weak van der Waals interlayer coupling and strong intralayer bonding. This review surveys the principal classes of 2D layered materials and systematically pairs each class with the low-frequency noise (LFN) spectroscopy studies performed on it mainly between 2013 and 2026. Unlike earlier material-specific reviews, it systematically compares the experimental device configurations, assigned microscopic mechanisms, and research gaps. The review also identifies specific research priorities.

Crystals doi: 10.3390/cryst16080541

Authors: Claudia Ciurel Ion Mitelea Ilare Bordeașu Dragoș Buzdugan Corneliu Marius Crăciunescu Ion-Dragoș Uțu

Cavitation erosion is a phenomenon that causes the degradation of engineering components operating in fluids under oscillating pressure, and it occurs through the repeated implosion of cavitation bubbles adjacent to the solid surface. This complex phenomenon involves both the hydrodynamic factors of the liquid and the properties of the material being eroded. Cavitation erosion tests were performed using a vibratory apparatus with piezoceramic crystals, in accordance with the ASTM G32-2016 standard. As a reference material, a wrought aluminum-based alloy in the hot-rolled condition, EN AW-6082, was selected. For both alloys, mass losses were measured and erosion rates were calculated. The eroded surfaces were examined by X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results indicate that the cavitation erosion resistance of the AZ 31B alloy in the hot-rolled condition is approximately 3.77 times lower than that of the reference material. This behavior is attributed to its lower hardness and heterogeneous microstructure, consisting of an α solid solution matrix with a hexagonal close-packed crystal structure and intermetallic particles of the Mg17Al12 type, which exhibit pronounced brittleness. Cavitation pits are observed mainly within the α-Mg solid solution grains and at the interfaces between the intermetallic phases and the α-Mg matrix.

Crystals doi: 10.3390/cryst16080540

Authors: Yi Gong Ying Gu Shan Jin Wenxian Yang Lifeng Bian Guifeng Chen Shulong Lu

Thermal degradation of InGaN quantum dots (QDs) during the temperature ramp for GaN quantum-barrier growth can compromise micro-light-emitting-diode active regions. Five-period InGaN/GaN QD structures with low-temperature-grown GaN (LT-GaN) caps of 0 nm (C0), 2 nm (C2), and 4 nm (C4) were studied. The nominal total GaN quantum barrier was fixed at 10 nm by adjusting the higher-temperature-grown GaN portion to 10, 8, and 6 nm, respectively. The active regions were characterized by high-resolution X-ray diffraction, aberration-corrected transmission electron microscopy, and temperature-dependent photoluminescence; post-ramp surface-reference specimens were examined by atomic force microscopy; and 10 μm × 10 μm micro-LEDs were evaluated by electroluminescence spectroscopy and integrating-sphere external quantum efficiency measurements. Compared with C0 and C2, C4 displayed clearer satellite reflections, more laterally continuous InGaN-rich contrast, and weaker thermal photoluminescence quenching; its surface reference also showed a more continuous terrace-like morphology with fewer fine depressions. The C4 micro-LED reached a peak external quantum efficiency of 4.45% at 20 A cm−2, compared with 2.58% at 150 A cm−2 for C0 and 1.80% at 140 A cm−2 for C2. Together, these results associate more effective thermal protection with a reduced relative contribution from defect-assisted nonradiative recombination and enhanced device efficiency.

Crystals doi: 10.3390/cryst16080539

Authors: Desheng Wang Xiufang Chen Guanglei Zhong Huiqing Chen Hongyu Shao Xuejian Xie Xianglong Yang Xiangang Xu Nan Xu Guojian Yu

High-purity SiC powder is an important feedstock for SiC crystal growth, but thermal-field regulation becomes difficult during large-batch synthesis. This study examined an α-SiC powder-synthesis furnace with upper and lower induction-coil groups through numerical simulations and 70 kg synthesis experiments. A representative two-dimensional axisymmetric model was used to compare eight cases with different coil-turn or numerical power allocations. Redistributing the coil turns changed E1, E2, volumetric Joule heat density, Q, and the resulting temperature and calculated gas-phase velocity-magnitude fields. From C01 to C04, the maximum calculated temperature decreased from 2501.10 to 2359.13 K, while ΔT decreased from 242.57 to 76.20 K. Increasing the upper-coil numerical power raised the temperature level while reducing ΔT to 152.41 K. Increasing the lower-coil numerical power also raised the temperature level, but increased ΔT to 292.26 K. Equal-total-power comparisons showed that axial power allocation affected Tmax and ΔT. XRD identified 6H-SiC as the detected crystalline phase in both analyzed middle-region specimens, although X-ray-amorphous carbon could not be excluded. The specimens also differed in macroscopic appearance, measured impurity concentrations, and local nitrogen concentration profiles. Because the experimental conditions were maintained nominally unchanged except for the upper-coil current, these specimen-level differences may be associated with altered internal thermal conditions. Such changes may affect local equilibrium, supersaturation, and species transport, providing a possible link to the observed material differences. The numerical results identify coil-turn allocation and axial power allocation as variables for regulating the calculated furnace fields.

Crystals doi: 10.3390/cryst16080538

Authors: Jiachen Xu Songbai Xue Yan Yang Dawei Zhu Xiaoxiao Zhou

Effects of varying lanthanum (La) content on the melting characteristics, spreadability, mechanical properties of brazed joints, and microstructure of low-silver BAg5CuZn brazing filler metal were investigated. The results indicate that the addition of La has little effect on the solidus and liquidus temperatures of the filler metal, while an excessive amount of La slightly raises its liquidus temperature. An appropriate amount of La enhances the spreadability of the filler metal on both copper and stainless steel plates and simultaneously inhibits grain growth, refining the microstructure of the BAg5CuZn-xLa filler metal. When the La content in the filler metal reaches 0.3%, the shear strength of the 304 stainless steel/304 stainless steel joint brazed with BAg5CuZn-xLa filler metal reaches 492 MPa, which is 17.7% higher than that of the brazed joint without the La addition.

Crystals doi: 10.3390/cryst16080537

Authors: Longchao Zhuo Hanyue Li Bingqing Chen Jiacheng Sun Zhaozong Zhang

Composition criteria for refractory high-entropy alloys (RHEAs) reliably predict whether a candidate composition forms a single-phase body-centred-cubic (BCC) solid solution, but not which BCC-confirmed composition will be strongest. Here we revisit seven previously reported RHEA compositions on freshly arc-melted material of our own, confirm each as single-phase BCC using full-spectrum X-ray diffraction re-indexing, and screen ten descriptors obtainable before mechanical testing against their room-temperature compressive yield strength: five compositional (mean atomic radius r−, mixing enthalpy ΔHmix, atomic-size mismatch δ, VEC, and melting point Tm), two lattice-scale (Nelson–Riley parameter a0 and Williamson–Hall apparent microstrain ε) and three microstructural (KAM, ELM15, and grain ECD). Only ΔHmix ranks the strengths, and its direction inverts the usual expectation: the less negative the mixing enthalpy, the stronger the alloy. Refractoriness carries no ranking information, and the most refractory member, NbMoTaW, is second weakest of six. At n = 6 only a perfect ranking reaches a Benjamini–Hochberg q below 0.05 across ten descriptors, so the q of 0.167 obtained here measures cohort resolution: a ranking of this magnitude clears the corrected threshold from eight alloys upwards. Mean atomic radius separately predicts a0 across all seven alloys.

Crystals doi: 10.3390/cryst16080536

Authors: João Vinícius Barros Reis Thiago dos Santos Ferreira João Marcos Oliveira Moura Salgado Costa Claudinei Santos Flávio Machado de Souza Carvalho Patrick de Lima Gomes Dolores Ribeiro Ricci Lazar Cecilia Chaves Guedes-Silva

Silicon nitride (Si3N4) is an advanced structural ceramic with considerable potential for load-bearing biomedical applications owing to its excellent mechanical properties and favorable biological response. In this study, the effect of wollastonite (CaSiO3) addition on the microstructure, mechanical performance, and in vitro bioactivity of Si3N4–CaSiO3 ceramic composites was investigated. Composites containing 5–30 wt.% wollastonite were prepared by pressureless sintering at 1800 °C for 1 h and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), density measurements, nanoindentation, Vickers hardness, fracture toughness, compressive strength, and simulated body fluid (SBF) immersion tests. Increasing the wollastonite resulted in progressive densification up to 20 wt.% CaSiO3, resulting in a maximum relative density of 96%, together with complete α→β-Si3N4 transformation and the development of elongated β-Si3N4 grains. The composition containing 20 wt.% wollastonite exhibited optimum mechanical performance, achieving a hardness of approximately 13 GPa, fracture toughness of ~5.5 MPa·m1/2, and compressive strength of ~2840 MPa. The results demonstrate that wollastonite plays a multifunctional role in Si3N4 ceramic composites by promoting densification during sintering and improving in vitro bioactivity while maintaining high mechanical performance. These findings highlight the potential of Si3N4–CaSiO3 ceramic composites as promising bioactive structural materials for load-bearing orthopedic and dental applications.

Crystals doi: 10.3390/cryst16080535

Authors: Yunxiao Jin Shixu Zhang Longping Luo Siqi Hong Jianmei Zhang

Freeze–thaw cycling can strongly disturb the pore-water environment, soil fabric, and contaminant mobility of heavy-metal-contaminated loess, thereby threatening the long-term effectiveness of stabilization treatments in seasonally frozen regions. This study investigated the coupled hydro-environmental and geotechnical performance of Pb-contaminated loess (untreated control group, CK) treated with microbially induced calcium carbonate precipitation (MICP), graphene (GR)-assisted MICP, and graphene oxide (GO)-assisted MICP under controlled freeze–thaw cycles. One-dimensional consolidation tests, toxicity characteristic leaching procedure (TCLP) tests, zeta-potential measurements, X-ray fluorescence (XRF), and scanning electron microscopy (SEM) were conducted to evaluate compressibility evolution, Pb leaching behavior, interfacial electrochemical characteristics, mineralogical changes, and microstructural mechanisms. After 9 days of mineralization, MICP reduced the Pb leaching concentration from 38.05 to 23.00 mg L−1, achieving a 39.55% reduction compared with untreated Pb-contaminated loess. Freeze–thaw cycling increased the susceptibility of treated loess to structural degradation and pore collapse, especially under medium to high vertical stresses. Nevertheless, the void ratio generally followed the order of CK > MICP > MICP + GR > MICP + GO under comparable loading and freeze–thaw conditions, indicating progressively enhanced resistance to compressive deformation. GR-assisted MICP showed an optimum dosage of approximately 1.0%, beyond which Pb leaching increased because of sheet restacking, agglomeration, and non-uniform biomineralization. In contrast, under up to 13 freeze–thaw cycles, GO-assisted MICP maintained the lowest void ratio and the most stable Pb immobilization performance among all treatments, demonstrating improved resistance against freeze–thaw-induced structural degradation. The results suggest that GO-assisted MICP can simultaneously improve Pb leaching control and soil-fabric stability, providing a promising low-carbon strategy for remediating heavy-metal-contaminated loess exposed to water-mediated freeze–thaw disturbance.

Crystals doi: 10.3390/cryst16080534

Authors: Caibao Guo Hai Gu Zhonggang Sun Jie Zhang Guoqing Dai

The Ti-6Al-4V alloy is widely used in aerospace and deep-sea applications due to its exceptional strength and corrosion resistance. However, its application is often constrained by high deformation resistance and a narrow hot-working temperature window, primarily attributed to its heat and mass transfer characteristics. To address these limitations, a novel Ti-6Al-1.3V-0.9Fe alloy was designed with an equivalent molybdenum content. In this study, Gleeble thermal simulation tests were conducted to investigate the impact of Fe on the hot deformation behavior under various conditions and to identify the optimal processing window for this alloy. The effects of deformation temperature and strain rate on the flow stress curves and peak stress were systematically analyzed, along with the role of Fe in microstructural evolution during hot deformation. The results demonstrate that the addition of Fe significantly refines the grain size of the Ti-6Al-1.3V-0.9Fe alloy. As expected, the flow stress decreases with increasing deformation temperature and increases at higher strain rates. Under high-temperature and low-strain-rate conditions, the alloy exhibits steady-state flow behavior, indicating improved hot workability. Based on the constitutive modeling, the apparent activation energy (Q) for hot deformation was calculated to be 503.81 kJ/mol. Finally, the optimal hot-working parameters for the Ti-6Al-1.3V-0.9Fe alloy were identified as a temperature range of 760 °C to 860 °C and a strain rate between 0.01 and 0.16 s−1.

Crystals doi: 10.3390/cryst16080533

Authors: Yunxi Zhu Yi Zhao Siying Li Zheyi Zhao Gexue Zhao

Carbonate jade has emerged as a recently recognized commercial variety in the Chinese gemstone market. Systematic gemological and mineralogical investigations on carbonate jade, however, remain very scarce. Three Xinjiang calcite-dominated jade samples were investigated by using Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, microbeam X-ray fluorescence (Micro-XRF) spectrometry, trace element analysis, in situ U-Pb dating, and C-O isotope analysis. The orange-red color originates from staining by hematite and magnetite inclusions, while the green color is produced by d-d electronic transitions of lattice-bound Fe3+ and Mn2+. The provenance comparison reveals systematic differences in trace element compositions between the Xinjiang carbonate jade and Pakistani Lvwen stone: the Xinjiang samples are characterized by extremely low Cu and Sr contents, whereas the Pakistani Lvwen stone has high Cu, Mn and Sr contents, and low Fe content. The U-Pb age obtained for the Xinjiang carbonate jade sample coincides with a Late Cretaceous rapid cooling event. Enriched light rare earth element (LREE) and C-O isotope (δ13CV-PDB = −1.19–2.21‰, δ18OV-SMOW = 15.00–20.01‰) signatures indicate that the carbonate-precipitating fluids were derived from marine carbonate wall rocks. These findings provide new mineralogical and geochemical constraints on the coloration mechanism, provenance, and fluid evolution of carbonate jade from Xinjiang.

Crystals doi: 10.3390/cryst16080532

Authors: Yujia Liu Ye Yuan Zheng Li Xinli Liu Zitong Zang Yang Liu Xianbo Nian Chunsheng Guo

The rapid development of wearable electronics has created a demand for flexible, lightweight, and sustainable power-supply technologies. The persistent temperature difference between the human body and the environment provides a low-grade thermal source for thermoelectric energy harvesting. However, traditional flexible thermoelectric devices still face limited self-supporting capabilities and difficulties in maintaining sufficiently low cold-side temperatures. Here, we designed a passively radiative-cooled thermoelectric film (PRT film) by integrating a PAM/PEDOT:PSS self-supporting thermoelectric composite layer with a polymer metamaterial radiative cooling (PMRC) film. The PAM/PEDOT:PSS layer serves as a self-supporting thermoelectric conversion component for harvesting low-grade heat, while the PMRC film layer acts as a passive cold-side regulator without energy input to lower the cold-side temperature and enhance the temperature gradient. By optimizing the PAM content, the PAM/PEDOT:PSS composite material with 85 wt% PAM achieved the highest power factor of 72.3 μW m−1 K−2. Under a temperature difference of 39 °C, the optimized PAM/PEDOT:PSS sample provided an open-circuit voltage of 0.47 V, a maximum output power of 1.1 μW, and a power density of 11.2 μW cm−2. According to the temperature-difference enhancement measured in experiments and the independently obtained load characteristics, the integration of PMRC films is expected to increase the maximum output power from 1.1 to 1.4 μW, with the corresponding power density rising from 11.2 to 14.25 μW cm−2, representing a 27.2% enhancement. This work demonstrates the feasibility of passive radiative cold-side regulation in enhancing low-level thermoelectric energy harvesting for wearable applications.

Crystals doi: 10.3390/cryst16080531

Authors: Guojun Yuan Yajun Gao Hongfang Li Lei Cheng Wenjuan Sun Haolu Sun

Transition metal phosphides (TMPs) have gained significant attention from researchers in the field of catalytic hydrogenation due to their excellent properties. However, existing studies have rarely explored the targeted regulation of the degree of crystal plane exposure of the Ni12P5 catalyst. It is difficult to significantly enhance the performance of this catalyst in the hydrogenation dechlorination (HDC) reaction of trichloroethylene by this strategy. This study proposes a regulatory approach: changing the ratio of ethylene glycol to water to precisely control the exposure ratio of the high-index (312) crystal plane of the Ni12P5 catalyst. Combined with the performance tests of trichloroethylene hydrogenation dechlorination at different reaction temperatures, the intrinsic relationship between the step atoms generated during the formation of the (312) crystal plane and the active sites of the catalyst was clarified. The study also utilized multiple characterization methods such as transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) to conduct a comprehensive property analysis of the prepared catalytic materials.

Crystals doi: 10.3390/cryst16080530

Authors: Xihui Liang Dah-An Luh

Angle-resolved photoemission spectroscopy (ARPES) clearly resolves surface-localized (SL) states, yet conventional density functional theory (DFT) band structures from slab calculations do not readily distinguish weakly confined SL states on surfaces such as Al(001), as traditional layer-threshold criteria fail for surfaces with long surface-state decay lengths. We establish a dual-criterion scheme using the surface ratio R and the localization integral L weighted by the inelastic mean free path (IMFP) to quantitatively distinguish SL states: R quantifies the surface-projected charge fraction, while L incorporates the photoelectron IMFP to mimic ARPES surface sensitivity, both evaluated within a fully converged 81-layer Al(001) slab that eliminates artificial inter-surface coupling. Band structures color-coded by R and L intuitively highlight SL states as bright yellow-white bands against red bulk backgrounds. Our calculations show that continuum SL features arise from multi-band hybridization (sharp surface resonances). Notably, R and L alone cannot separate absolute surface states from resonances. All DFT calculations were performed using the PBEsol exchange-correlation functional within the GGA framework, the PAW formalism, and an 81-layer Al(001) slab model. This work reveals the electronic nature of surface features on Al(001) and provides a quantitative SL-state identification tool that is conceptually transferable to other crystalline surfaces.

Crystals doi: 10.3390/cryst16080529

Authors: Yuxin Liu Wenhui Tong Xinyu Wu Jiale Li

Microstructural evolution and mechanical properties of as-extruded Mg-2.5Si-4Zn-0.7Ca-1Y alloys were characterized under diverse heat treatment conditions. An optimal regime of 200 °C for 12 h emerged, delivering a peak Vickers hardness of ~100 HV0.2. After heat treatment, substantial dissolution of Zn into the α-Mg matrix occurred and Ca/Y-rich intermetallics underwent spheroidization. The microstructural changes facilitated the improvement of ultimate tensile strength (UTS) at 200 °C from ~160 MPa to ~200 MPa, while the elongation decreased from ~18% to ~6%. The enhanced high-temperature strength derives from Zn solid-solution strengthening and spheroidization of the Ca/Y-rich network phase, with a possible additional contribution from Y redistribution near the Mg2Si-containing regions.

Crystals doi: 10.3390/cryst16080528

Authors: Longchao Zhuo Yingliang Zhang Bingqing Chen Jiacheng Sun Hao Wang Zhaozong Zhang

Refractory high-entropy and compositionally complex alloys are routinely compared by nominal composition and as-processed phase, yet processing changes the material that is actually tested. This is a critical, mechanism-led narrative review rather than a systematic review; the databases, complete search strings, screening sequence, inclusion and exclusion criteria, and evidence-grading rubric are reported so that coverage and selection bias can be assessed independently. This review synthesizes 186 publications around the NbTaV compositional core and compares alloys through directly measurable features of the processed state: interstitial content, local chemical order, grain-boundary chemistry, defect and grain architecture, phase morphology, compositional gradients and surfaces. Every source is assigned to a compositional tier and graded along four evidence axes: 96 of the 186 sources report Nb–Ta–V-containing states (Tier I), 58 are body-centered cubic refractory comparators (Tier II) and 32 are transferred-mechanism analogues (Tier III), and only 14 Tier I sources supply direct tensile, fracture or tensile-creep measurements. This asymmetry, rather than any disagreement between compositions, is the field’s binding evidence constraint. Direct tensile, fracture, and creep measurements are kept separate from compression, hardness, calculation, and screening evidence. This separation reconciles observations that otherwise appear to conflict: oxygen can strengthen or embrittle; lattice distortion can raise strength while lowering dislocation mobility; local order can harden the alloy, redirect defects or precede decomposition; and second phases help only within morphology- and service-specific compatibility windows. The strongest tensile behavior is obtained when mobile plasticity carriers are preserved, and interstitials, interfaces and phase continuity are simultaneously controlled. High-temperature, environmental, and irradiation performance depend additionally on the transition from the as-manufactured condition to the state that evolves during service. Quantitative matching tolerances for the convergent-state falsification test, service-condition-specific validation hierarchies, ordinal scoring rules for the phase-compatibility map, and a source-level audit of every quantitatively compared value are provided so that the framework can be tested and the synthesis independently checked.

Crystals doi: 10.3390/cryst16080527

Authors: Taswar Iqbal Soon-Ku Hong Sung Beom Cho Trong Si Ngo Raouf Hayyak Mee-Hi Choi Moonkyong Na Young Heon Kim

A comprehensive beyond density functional theory study of the structural, energetic, and electronic properties of the technologically most relevant SiC polytypes 3C, 2H, 4H, and 6H-SiC, together with the single Shockley-type stacking fault (1SSF or 31SSF) in 4H-SiC, was conducted. Lattice constants computed at the PBEsol and HSE06 level match experimental values within 0.1% accuracy. Total energies evaluated at the random-phase approximation level yield a physically consistent hierarchy of polytypes with 3C-SiC as the most stable phase, which is in agreement with low-temperature experimental results. Quasiparticle band gaps computed with both the single-shot G0W0@PBE and the partially self-consistent GW0@PBE formulations quantitatively match well with the experimental values. The band structure of 31SSF reveals fault-induced sub-gap band splitting at the M point of 0.21 eV at the GGA level, which increases to 0.28 eV upon G0W0 correction. To our knowledge, this provides the first GW-level treatment of the 31SSF electronic structure in 4H-SiC. These results collectively provide a many-body perturbation theory (MBPT) level reference dataset for SiC polytypes and the commonly found stacking fault in 4H-SiC.

Crystals doi: 10.3390/cryst16080526

Authors: Hetao Huang Mingfei Gao Zhengju Liu Guanyu Chen Chaoli Jiang Zhiliang Cheng

Cooling crystallization of DL-methionine requires the joint control of crystallization yield and bulk density because operating conditions that favor one response may impair the other. Here, single-factor experiments, Plackett–Burman screening, and a three-factor Box–Behnken response-surface design were combined to identify a local operating window. Stirring speed, crystallization time, and solution pH were retained for response-surface modeling. The quadratic models for crystallization yield and bulk density were significant, with R2 values of 0.9910 and 0.9892, respectively, and nonsignificant lack-of-fit terms. Multi-response optimization selected a stirring speed of approximately 332 r/min, a crystallization time of 1.47 h, and a pH of 5.55. Three validation experiments produced yields of 48.98–49.57% and bulk densities of 0.2925–0.3035 g/mL, with relative errors below 5% compared with the model predictions. X-ray diffraction showed no detectable change in the principal DL-methionine crystal phase across representative products. X-ray photoelectron spectroscopy further showed closely matched near-surface C 1s, N 1s, O 1s, and S 2p features between the raw material and the product obtained under the optimized conditions. The sodium nitroprusside assay gave total methionine contents of 99.64–99.79% for the raw material and five representative products; for the model-selected product, the colorimetric result (99.79%) agreed with the amino acid analyzer result (99.93%) to within 0.14%. The combined PB–BBD/RSM workflow therefore supports local parameter selection within the tested design space while maintaining the principal crystal phase, near-surface chemical-state profile, and total methionine content of the recovered product.

Crystals doi: 10.3390/cryst16080525

Authors: Tatyana Ivanova Antoaneta Harizanova Nikolay Petkov

In the present work, thin TiO2 films were obtained by the sol–gel spin-coating method on glass and ITO-covered glass substrates. The crystallization evolution of the thin films was studied by the X-ray Diffraction (XRD) technique. The results indicate that the films’ crystalline structure was greatly affected by substrate type. X-ray photoelectron spectroscopy (XPS) revealed the chemical states of the TiO2 films and proved the formation of TiO2 on ITO substrates. Field Emission Scanning Electron Microscopy (FESEM) showed that the TiO2 films deposited on the ITO glass possessed a uniform and homogeneous surface morphology. The influence of optical properties (transmittance, reflectance, and optical band gap) on substrate type, the number of layers and annealing temperatures was determined. Spectroscopic data confirmed high transparency of the TiO2 films obtained on ITO substrates as the transmittance in the visible spectral range was close to 85%. The obtained results reveal that thin TiO2 films on ITO substrates can be an excellent candidate for photovoltaic and optoelectronic applications.

Crystals doi: 10.3390/cryst16080524

Authors: Fawei Wang Jiapeng Wang Zihu Wang Jianhua Wang Yucun Liu

To avoid potential misinterpretation, the caption of Figure 6 and the text preceding it have been revised to clearly indicate that Figure 6a displays the sulfate salt of compound 1 [...]

Crystals doi: 10.3390/cryst16080523

Authors: Jingying Lv Qingfeng Guo Shuo Ran Xin Zhang

Natural blue calcite is relatively rare, and its coloration and luminescence mechanisms have not been systematically established. In this study, four natural blue calcite samples from China were comprehensively characterized using mineralogical testing, X-ray diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet–visible spectroscopy (UV-Vis), photoluminescence (PL), and electron paramagnetic resonance (EPR). XRD confirms single-phase trigonal calcite (space group R-3c). EPMA detects minor Mg, Fe, Cu, and Sr, with smaller-radius Mg2+, Fe2+, and Cu2+ being the main contributors to the contraction through isomorphous substitution for Ca2+. UV-Vis spectra show characteristic absorptions at 270 nm and 340 nm related to lattice defects with a broad emission band centered at 480 nm in the PL spectra. EPR detects a CO2− radical center (g = 2.003), and the same signal is also observed in the colorless sample. The colorless sample also contains the same CO2− radicals, indicating that these radicals alone do not account for the blue coloration. A broad 480 nm blue-violet fluorescence band is observed in the four blue samples under 405 nm excitation. These findings provide a spectroscopic and crystallographic basis for distinguishing natural blue calcite from analogous materials and for understanding the origin of its color and luminescence.

Crystals doi: 10.3390/cryst16080522

Authors: Xiangcao Li Baoan Liu Hongjie Xue Yuan Xie Xin Ju

This study used time-of-flight secondary ion mass spectrometry (TOF-SIMS) to comprehensively analyze the elemental composition, ion distribution, and signal variations in potassium dihydrogen phosphate (KDP) crystals at various sputtering depths after laser irradiation. Positive ion mass spectra were employed to identify the characteristic ions K+, Ca+, Fe+, Si+, and P+. These ions were assigned to their corresponding chemical species. Large-area two-dimensional chemical mapping and maximum count/total count (MC/TC) analysis combined and showed clear depth-dependent trends; all detected ions had significantly higher MC and TC values at larger sputtering depths. At a depth of 1.3 nm, Fe-related and O-related ion signals exhibited overlapping localized hotspots, whereas Ca species showed ring-like enrichment at the edges of the damage pits. These changes are attributed to the laser-induced decomposition of KDP crystals, in which metal inclusions absorb laser energy, generate localized high temperature and pressure, and promote material ejection and ion redistribution. These findings provide direct experimental evidence for understanding laser-induced elemental redistribution in KDP crystals and offer useful guidance for further optimization of their performance.

Crystals doi: 10.3390/cryst16080521

Authors: Sanjie Liu Zilong Zeng Yongyong Cao Zhenyi Deng Xinjie Li Zixin Liang Rongjie Feng Jiaping Long Yu Liu Ruifan Tang Xinhe Zheng

Group III-nitride semiconductors (GaN, AlN, InN) serve as foundational materials for modern optoelectronics, high-frequency microelectronics, and next-generation energy harvesting devices. However, traditional high-temperature epitaxy (>700 °C) introduces severe thermal stress, high dislocation densities, and fundamental incompatibility with flexible substrates or CMOS back-end-of-line (BEOL) processes. Plasma-enhanced atomic layer deposition (PEALD) provides a disruptive, ultra-low thermal budget (<300 °C) pathway for atomic-scale precision growth and conformal coating. This review systematically summarizes recent frontiers in PEALD-synthesized Group III-nitrides and 2D/3D polar heterostructures. First, we dissect the microscopic nucleation kinetics, surface bond reconstruction, and impurity suppression mechanisms across diverse substrates, including Si, sapphire, quartz, metals, and flexible polymers. Next, we highlight 2D template-assisted van der Waals epitaxy on graphene and MoS2, and elucidate polarization-driven dipole interactions and band alignment engineering at 2D/3D polar interfaces (e.g., α-In2Se3, Janus MoSSe). Furthermore, we comprehensively discuss innovative applications in advanced photovoltaics (as electron transport and passivation layers in perovskite and quantum dot-sensitized solar cells), silicon-based microcavity lasers, high-electron-mobility transistors (HEMTs), and flexible multimodal sensors. Finally, key technological challenges—including the low-thermal-budget paradox, wafer-scale uniformity, and deposition throughput—are addressed alongside future perspectives in area-selective ALD and neuromorphic computing, presenting a cohesive blueprint from underlying physics to macroscopic system integration.

Crystals doi: 10.3390/cryst16080520

Authors: Changjiang Nie Hengxue Wang Zhihong Chen Junyan Wang Huaqing Xiao Yang Liu

The structural phase transition and associated orientational domain configurations in perovskite-type BixCa1−xMnO3 ceramics were investigated in this work. A series of BixCa1−xMnO3 solid solutions with x = 0.05, 0.25, 0.33 were synthesized, and Bi0.25Ca0.75MnO3 with moderate orthorhombic lattice distortion was selected as the representative sample for systematic TEM characterization. Upon cooling from high temperature, the material undergoes a symmetry-lowering transition from the cubic phase with Pm3¯m space group to the orthorhombic phase with Pnma space group. Selected-area electron diffraction (SAED) and bright-field TEM observations reveal the formation of multiple orientational domains, including both 90° and 120° configurations, within individual grains. High-resolution TEM (HRTEM) further confirms the coexistence of three distinct domain orientations at the atomic scale, with well-defined lattice fringes and domain boundaries. The reciprocal-space orientational relationships derived from SAED patterns demonstrate that these domains originate from the symmetry breaking of the parent cubic lattice during the phase transition. These findings provide direct crystallographic insight into the domain structures of BCMO, and such microstructural features are essential for revealing the structural stability and intrinsic functional behaviors of BCMO manganites.

Crystals doi: 10.3390/cryst16080519

Authors: Junting Mu Siying Li Yi Zhao Gexue Zhao Zheyi Zhao

Rutile is an oxide mineral widely distributed in igneous, metamorphic, and sedimentary rocks; it crystallizes in the tetragonal system. Trace-element abundances in rutile are influenced by the host-rock composition, redox conditions and crystallization history. Rutile exhibits high refractive index, strong dispersion, and adamantine luster. Its enrichment in high field strength elements (HFSEs) can be used to trace its formation environment. Owing to its inclusion-poor, compositionally uniform characteristics, rutile is particularly well-suited to in situ U-Pb geochronology. By integrating spectroscopic analysis, trace-element geochemistry, and U-Pb geochronology, this study systematically characterizes nine rutile samples from Madagascar, Pakistan, and Brazil, establishing a multi-dimensional scheme for origin discrimination. Spectroscopic analyses reveal that the infrared reflection band near 670 cm−1 varies systematically with provenance. It appears as a broad, strong band in Madagascar samples, becomes weaker and narrower in Brazilian samples, and is partially absent in Pakistani samples. The Eg Raman mode of Brazilian rutile is slightly left-shifted and exhibits lower intensity, indicating a distinct lattice strain state. Analyzed samples occupy well-separated compositional fields on Nb–V, V–Ta, Zr–Hf and Nb–Ta binary variation plots. Specifically, Pakistani samples are characterized by high Nb and Ta contents and relatively lower V contents than the Brazilian and Madagascar samples. Madagascar samples show pronounced W enrichment and very low Cr. Brazilian samples display elevated Cr, V, higher U contents and more radiogenic Pb isotope compositions. Zr–W systematics and Cr–Nb bivariate discrimination allow inference of geological genesis. The Madagascar rutile is of hydrothermal origin, whereas the Pakistani and Brazilian rutile are metamorphic, derived from felsic/pelitic and mafic protoliths, respectively. LA-ICP-MS U-Pb geochronology yields a lower-intercept age of 504 ± 13 Ma (MSWD = 1.1) for the Madagascar sample (MD-1). This concordant, low-common-Pb age corresponds to the Pan-African orogeny and suggests strong potential as an in-situ U-Pb dating reference material. The Brazilian and Pakistani samples yield lower-intercept ages of 486 ± 53 Ma and 36.8 ± 2.9 Ma, respectively. However, the larger data scatter precludes their use as reference materials.

Crystals doi: 10.3390/cryst16080518

Authors: Jiajun Feng Qiuhua Huang Caiyuan Wen Kunlin Wang Shiting Chen Keyi Fang Peixuan Chen Lianfen Chen Xiang Li

Garnet-structured compounds have long been recognized as versatile host platforms for luminescent phosphors, owing to their robust chemical stability and highly tunable cationic sublattices. Conventional aluminate and gallate garnets, however, generally face intrinsic limitations, including severe concentration quenching at high dopant levels, relatively high phonon energy, and unsatisfactory efficiency for long-wavelength near-infrared (NIR) emission. In recent years, sodium-based germanate garnets, constructed by introducing aliovalent Na+ into dodecahedral sites combined with Ge4+ substitution in tetrahedral frameworks, have emerged as a promising branch of garnet phosphors. The aliovalent Na+ incorporation brings unique structural effects, including energy migration blocking, coordination environment distortion, and defect level modulation, which endow the materials with advantages in mitigating concentration quenching, boosting energy transfer efficiency, and enhancing thermal stability. This review systematically summarizes the crystal structure classification and luminescence fundamentals of sodium-based germanate garnet systems, and introduces mainstream synthesis techniques represented by the high-temperature solid-state method. Focusing on representative host systems, the luminescence characteristics and energy transfer mechanisms of both rare earth- and transition metal-doped systems are elaborated in detail, followed by a summary of four representative performance regulation strategies: cationic disorder engineering, crystal field engineering, defect engineering and dual-site cooperative regulation. The multifunctional applications of these materials in white light-emitting diodes, plant growth lighting, fluorescence temperature sensing, NIR imaging, and information encryption are also presented. Finally, existing challenges and future research perspectives are proposed to provide guidance for the development of high-performance garnet phosphors.

Crystals doi: 10.3390/cryst16080517

Authors: Cristian E. Botez Zachary Musslewhite Alex D. Price Chunqiang Li

We used powder X-ray diffraction (XRD) and ac impedance spectroscopy to investigate the polymorphic phase transitions undergone by the MH2PO4 (M = Cs, K, Rb) proton conductor series upon heating. High-pressure methods used in conjunction with energy dispersive XRD enhanced by synchrotron radiation allowed us to isolate a pure cubic (superprotonic) RbH2PO4 (RDP) polymorph (at P = 1.2 GPa and T = 320 °C) and collect data of enough quality to Rietveld refine its crystal structure. Our data and analysis reveal that cubic RDP (Pm-3m, a = 4.76 ± 0.01 Å) is described by a unit cell where Rb and P atoms are in (0, 0, 0) and (0.5, 0.5, 0.5) positions, respectively, whereas O atoms are in (0.5, 0.234(5) 0.342(6)) positions having a multiplicity of 24 and an occupancy of 0.166. This results in dynamically disordered PO4 tetrahedra that enables the superprotonic conduction in RDP, a mechanism like the one in the high-temperature cubic phase of the Cs-based compound CsH2PO4 (CDP). This is a notable behavior, as RDP and CDP are structurally different at room temperature—RDP is tetragonal (I-42d) and CDP is monoclinic (P21/m)—but following polymorphic modifications upon heating they both end up in superprotonic cubic phases that are isostructural to one another. On the other hand, we found that although the K-based phosphate KH2PO4 (KDP) has the same crystal structures as RDP at room and at intermediate temperatures, further heating does not lead to a cubic KDP phase. Overall, our results are significant from both the fundamental and applied perspective as superprotonic phosphates are promising materials for fuel cell electrolyte applications.

Crystals doi: 10.3390/cryst16080516

Authors: Luyan Jiang Qingfeng Guo Can Cui Nannan Wang

Three commercial red–white banded rhodochrosite samples sold as Argentine “Rosa del Inca” material were investigated using conventional gemological observation, mineralogical analysis, micro-area chemical analysis, and spectroscopy. The red and white bands differ in color, transparency, and microstructure. However, both bands are mainly rhodochrosite. No evidence indicates that calcite, dolomite, or other Ca-bearing carbonate minerals are the main phases in the white bands. Representative EPMA analyses of LMK-02 show that the analyzed white-band points tend to contain slightly lower Mn and relatively higher Fe and Mg than the red-band points, while CaO is below the detection limit at all representative EPMA positions. Micro-XRF mapping of LMK-02 reveals only local and discontinuous enrichments of Ca and Zn; however, the mineralogical identity and occurrence mode of these enriched domains remain unresolved. Combined with the EPMA data, the XRD, FTIR, Raman, and UV–Vis results do not support marked Ca enrichment, extensive Ca substitution for Mn, or abundant Ca-bearing carbonate phases in the analyzed white bands of LMK-02. Instead, the results indicate Ca-poor compositional variation within rhodochrosite, with the representative EPMA data showing a descriptive tendency toward slightly lower MnO and relatively higher FeO and MgO contents in the analyzed white-band points.

Crystals doi: 10.3390/cryst16080515

Authors: Ioan Ovidiu Pană Simona Guțoiu Sanda Boca Maria Suciu Răzvan Hirian Maria Olimpia Miclăuș Septimiu Cassian Tripon Cristian Leoștean Lucian Barbu

Nanostructured copper oxide (CuO) holds significant promise for optoelectronic, photocatalytic, and biomedical applications, yet its performance is critically dictated by its morphology, crystallite size, and surface chemistry. In this work, pure monoclinic CuO nanoparticles were successfully synthesized via a facile, kinetically controlled aqueous co-precipitation route using three distinct precursor salts: copper acetate (CO-Ac), copper sulfate (CO-S), and copper chloride (CO-Cl). To achieve precise architectural control, the synthesis was conducted near the thermodynamic solubility limit of the precursors combined with an abrupt NaOH injection, effectively decoupling the nucleation stage from crystal growth. Rietveld refinement of X-ray diffraction (XRD) data confirmed the structural integrity of the monoclinic lattice across all samples, χ2 = 1.04 − 2.02, crystallinity 53–55%, while demonstrating that the precursor anion strongly governs the volume-averaged crystallite size, which expanded from 16 nm (CO-Ac) to 30 nm (CO-S) and 52 nm (CO-Cl). Morphological analyses revealed that acetate acts as a non-specific capping ligand, promoting isotropic, quasi-spherical nanoparticles that aggregate into high-surface-area (69.04 m2/g) “bead-chain” assemblies. Conversely, sulfate and chloride ions act as shape-directing agents via facet-selective adsorption on nucleation seeds, yielding two-dimensional plates and anisotropic acicular/needle-like architectures, respectively. X-ray photoelectron spectroscopy (XPS) and modified Auger parameter (α ~1851 eV) analyses confirmed the absolute dominance of Cu2+ states, with a minor fraction (~2.5 mol %) of lower-coordinated surface edge states. XPS further unveiled that the strongly alkaline environment (pH ~14) drives precursor-dependent surface chemistry: CO-Ac nanoparticles retain a clean, hydroxylated layer with minor acetate residues, whereas CO-S and CO-Cl samples develop a passive copper hydroxycarbonate (Cu2(OH)2CO3) surface barrier that blocks active sites and reduces porosity. Optical properties analyzed via UV-vis diffuse reflectance revealed a pronounced, size-dependent blueshift relative to bulk CuO, with fundamental indirectly allowed bandgaps of 2.6 eV, 2.36 eV and 1.93 eV for CO-Ac, CO-S and CO-Cl samples, while the direct bandgaps shifted from 3.0 eV, 3.2 eV, and 3.57 eV for the mentioned samples. This behavior is attributed to quantum confinement governed by fine individual nanocrystals. These findings establish that precursor engineering offers a robust pathway to tailor the morphological, optical, and interfacial properties of CuO nanostructures for targeted functional devices.

Crystals doi: 10.3390/cryst16080514

Authors: Chuyue Yang Jizhe Lyu Xunning Cao Xiaoqiang Liu

To evaluate whether atmospheric-pressure plasma jet (APPJ) treatment induced early, sintering-related, surface microstructural variations in 3 mol% yttria-stabilized zirconia (3Y-TZP), with a particular focus on how treatment time affected the grain size and SEM-derived surface dark-area fraction, this exploratory study examined time-dependent surface microstructural changes in commercial 3 mol% yttria-stabilized zirconia (3Y-TZP) subjected to air APPJ exposure for 4, 8, 15, 30, or 60 min under fixed device settings. A separate no-dwell furnace reference series was used to contextualize surface microstructural changes during heating; it was not used to assign an equivalent temperature to APPJ exposure. Field-emission scanning electron microscopy was used to determine surface grain dimensions and a threshold-derived surface dark-area fraction. No specimen-surface temperature was recorded during APPJ exposure. Surface grain dimensions remained similar through 15 min and increased at 30 and 60 min, whereas the surface dark-area fraction changed modestly. Under the tested conditions, prolonged APPJ exposure was associated with marked surface grain coarsening and limited change in the SEM-derived dark-area fraction.

Crystals doi: 10.3390/cryst16080513

Authors: Erika Griesshaber Sebastian Hoerl Miguel A. Godoy-Bermúdez Daniel Weller Carmen Salas Alejandro Rodríguez-Navarro Antonio G. Checa Wolfgang W. Schmahl

Scaphopod molluscs are marine, infaunal, cosmopolitan animals. They encase their soft tissue with an aragonitic tusk-shaped shell that has at its two ends an orifice, the aperture and the apex. We investigated the shell of the dentaliid species Fissidentalium metivieri and Antalis weinkauffi and characterized shell crystal organization with electron backscatter diffraction (EBSD) and laser confocal and scanning electron microscopies. Based on crystal size, morphology, organization and growth-line spacing, we distinguish five different crystal arrangement motifs in the investigated shells. We find two slightly different microstructures for the shell proper, two microstructures for the attachment of muscles to the shell and one microstructure for a secondary hard tissue growth product, secreted at the apical orifice. Crystal organization motifs are crossed-lamellar, dendritic and prismatic. Crystal textures are crossed-lamellar, axial-like and crossed-lamellar-like. Crystal organization with a crossed arrangement is utilized for shell formation by representatives of many Ca-carbonate shell-secreting mollusc classes/subclasses: Scaphopoda, Gastropoda, Bivalvia, Polyplacophora (crossed-lamellar), and Patellogastropoda (crossed-foliated). Based on structural–crystallographic attributes, we highlight a basic shell structure that is broadly similar for the species of these mollusc classes/subclasses. However, this basic crystal arrangement motif is significantly modulated by the specific crystal organization that is inherent for a particular mollusc class/subclass.

Crystals doi: 10.3390/cryst16080512

Authors: Geng Cao Shaopeng Wu Dongxin Wang Zhaopeng Yang Lipeng Yang Xixi Su

Be–Al alloys are attractive for aerospace and precision-engineering applications because of their low density, high specific stiffness, and excellent dimensional stability. However, their broader application is constrained by multiscale defects arising from the low mutual solubility of Be and Al, their large melting-point difference, and the high reactivity of the Be/Al interface. This review critically examines defect formation and microstructural evolution in Be–Al alloys produced by casting, powder metallurgy, pressure infiltration, thermomechanical processing, and additive manufacturing, with particular emphasis on additive manufacturing. Rapid solidification can refine the Be-rich phase and suppress coarse segregation, but unstable melt-pool behavior, restricted gas escape, cyclic thermal loading, and insufficient interfacial diffusion may also promote porosity, compositional heterogeneity, residual stress, and interfacial degradation. The mechanical properties of Be–Al alloys depend strongly on Be-phase morphology, continuity of the Al matrix, interfacial integrity, and the spatial distribution of processing-induced defects. Recent progress in alloy design, process optimization, interfacial engineering, and post-processing is evaluated, together with the limitations of the available evidence. Future research should establish quantitative processing–defect–microstructure–property relationships through in situ monitoring, multiscale characterization, predictive modeling, and standardized mechanical validation. These advances are essential for the reliable manufacture of complex, high-performance Be–Al components.

Crystals doi: 10.3390/cryst16080511

Authors: Mathias Mørch Amalie Povlsen Laursen Jack Thomas-Hunt Priyank Shyam Mogens Christensen

The formation of W-type hexaferrite magnets was investigated using in situ synchrotron X-ray powder diffraction. Both the holding time and precursor composition were investigated to evaluate the effect on phase purity and crystallite size using Rietveld refinements. Based on the refinements, it was found that the formation of W-type hexaferrites initiates shortly after reaching 1200 °C and happens within a few seconds. M-type hexaferrite was formed at a lower temperature before being transformed into W-type hexaferrite. Despite the short holding times, at elevated temperatures, the crystallite sizes along the a,b-axis exceeded the detection limit of the powder diffraction data, as the peak widths associated with the a,b-planes became too narrow to resolve changes as function of time. Magnetization data recorded from the in situ prepared samples revealed a higher saturation magnetization in the W-type hexaferrites relative to conventional M-type hexaferrites. No appreciable coercivity was found, which can be attributed to different effects: (1) reduced anisotropy constant, (2) large crystallite growth resulting in multi-domain crystallites, or (3) exchange-coupling with soft spinel ferrite found in the sample. Based on this study, we conclude that W-type hexaferrites can be formed after a few seconds at 1200 °C and that crystallite growth happens subsequently after the formation of the W-type hexaferrite structure.

Crystals doi: 10.3390/cryst16080510

Authors: Yaojia Ren Jiajun Xu Yingkang Wei Yingying Liu Jilei Zhu Shifeng Liu

Correction 1: Abbreviation error [...]

Crystals doi: 10.3390/cryst16080509

Authors: Jinguo Wang Lei Yang Gang He Zhanggui Hu

In this work, LiF was introduced as a flux additive to overcome the high viscosity challenge of the self-flux system, which successfully grew a large-scale cesium lithium borate (CLBO) single crystal with dimensions of 136 × 132 × 68 mm3 and a weight of 1275 g via the top-seeded solution growth (TSSG) method. The as-grown crystal showed an optical transmittance of over 90% in the spectral range of 230–1880 nm and an extremely low absorption coefficient of 2.8 ppm/cm at 1064 nm. Notably, under 120 W pumping at a high repetition rate of 2 MHz, the fabricated CLBO optical element achieved a record-high 266 nm output power of 26.1 W with an optical conversion efficiency of 21.75%. Moreover, the laser system maintained stable continuous operation at >23 W for over 120 h.

Crystals doi: 10.3390/cryst16080508

Authors: Zhixuan Xue Dongzhi Hou Lei Chen Ziyu Su Jixiang Liang Shanding Ma Zhou Li Kun Yang Yanhui Sun Chao Chen

The presence of ferrite in 316 austenitic stainless steel affects its magnetic permeability, and the secondary precipitates formed by ferrite decomposition can further degrade the corrosion resistance, limiting its application in industries such as nuclear power and medical devices. In previous studies, the characteristics of ferrite and precipitates in several 316 stainless steel continuous-casting billet samples with different Ni contents were analyzed. In this work, remelting experiments were further conducted on several 316L stainless steels with different Ni contents using a tube furnace; according to the Ni content, they are designated as L-316, M-316, and H-316 stainless steels. Metallographic analysis and electron back-scattered diffraction (EBSD) characterization were employed. The effects of Ni content and cooling rate on the microstructure of 316 stainless steel were systematically investigated. The results show that for the L-316 stainless steel, the ferrite morphologies in water-cooled, oil-cooled, air-cooled, and furnace-cooled samples change successively as follows: skeletal and lath-like, clustered network, lath-like and clustered network, and short rod-like. For the M-316 stainless steel remelted samples, the ferrite morphologies are network and skeletal, network and short rod-like, semi-network and short rod-like, and semi-network, respectively. The solidification modes of the L-316, M-316, and H-316 stainless steel remelted samples are FA, FA, and AF modes, respectively. Increasing Ni content reduces the ferrite content under all cooling conditions. When the Ni content increases from 10% to 12.17%, the ferrite content decreases significantly, with a greater reduction at higher cooling rates; when the Ni content further increases to 14.25%, the decrease in ferrite content slows down, indicating that after Ni content reaches a certain level, its inhibiting effect on ferrite formation weakens. The effect of cooling rate on ferrite content depends on the solidification mode: in the FA mode, slow cooling promotes diffusional transformation of ferrite to austenite, so the ferrite content decreases with decreasing cooling rate—for L-316 stainless steel, the ferrite content drops from 22.44% in the water-cooled sample to 2.71% in the furnace-cooled sample. In the AF mode, slow cooling favors the enrichment of elements at grain boundaries and promotes ferrite nucleation and growth; the overall trend of ferrite content increases as the cooling rate decreases. For the H-316 stainless steel specimens, the ferrite content is similar between water-cooled specimens (0.36%) and oil-cooled specimens (0.26%); for air-cooled specimens, the ferrite content increases significantly to 1.49%; and finally, it reaches 1.94% for the furnace-cooled specimen. Regarding secondary precipitates, the phase constituents of the L-316 stainless steel specimens after water cooling, oil cooling, and air cooling consist of an austenite matrix and ferrite, with a secondary precipitated Chi phase forming only under furnace cooling conditions. For the M-316 stainless steel, the Sigma phase and Chi phase begin to form under oil cooling conditions, and the Sigma phase also precipitates in the oil-cooled specimens of the H-316 stainless steel. In the air-cooled and furnace-cooled specimens of both M-316 and H-316 stainless steels, the secondary precipitated phase is the Sigma phase. All three types of water-cooled stainless steel specimens exhibited no secondary precipitate phase; increasing the cooling rate suppresses atomic diffusion, thereby reducing the precipitation of Chi phase and Sigma phase; however, a higher Ni content shifts the solidification mode toward the AF mode, making secondary precipitates more prone to form.

Crystals doi: 10.3390/cryst16080507

Authors: Katarina Bolko-Seljak Ilenia D’Abbrunzo Beatrice Perissutti

The solid-state landscape of pharmaceutical compounds is often characterized by the occurrence of polymorphs, hydrates, and solvates, which may significantly influence their physicochemical and biopharmaceutical properties. In contrast, some active pharmaceutical ingredients exhibit a remarkable resistance to crystal form diversification, despite extensive experimental investigation. In the present work, vinpocetine was subjected to an extensive solid-form screening campaign aimed at exploring its propensity to generate alternative polymorphs, hydrates, and solvates. Mechanochemical experiments were performed under neat grinding and liquid-assisted grinding conditions using a broad range of organic solvents and water, including two-step milling procedures and formulations containing surfactants. Additional investigations included high-energy planetary milling, high-pressure compaction, exposure to controlled humidity, thermal cycling, slurry-bridging experiments in various media, and crystallization after mechanochemical neutralization of vinpocetine salts. The resulting solids were systematically characterized by powder X-ray diffraction, and thermal and morphological analyses. In all cases, the recovered solid corresponded to the commercially available crystalline form of vinpocetine, with no evidence of alternative polymorphs, solvates, or hydrates. These results demonstrate the unusual robustness of vinpocetine crystal structure across a wide range of mechanical, thermal, and solvent-mediated conditions. Notably, this behavior contrasts with the well-established ability of vinpocetine to form numerous salts and salt cocrystals, suggesting that solid-state diversification in this compound is primarily driven by proton-transfer processes rather than by neutral polymorphism or solvent incorporation. The present study provides experimentally defined boundaries for the solid-state landscape of vinpocetine and contributes valuable data for future crystal-form prediction and pharmaceutical development studies. Beyond the specific findings reported herein, the systematic documentation of both successful and unsuccessful experimental outcomes represents a valuable source of experimentally validated positive and negative data that may support the future development and validation of AI-assisted crystal-form prediction tools.

Crystals doi: 10.3390/cryst16080506

Authors: Kenya V. Medina Juan L. Pinedo Katia Campos Callah Preti Kenya Rosas Erick Morales Orrante Josemaria S. Soriano Hadi D. Arman Pius O. Adelani

The condensation reaction of pyromellitic dianhydride and (aminomethyl)phosphonic acid in imidazole yielded N,N′-bis(phosphonomethyl)pyromellitimide ([(H2O3P)CH2-(C10H2N2O4)-CH2(PO3H2)]∙2H2O). Recrystallization of this compound from deionized water, by placing the solution in a desiccator to allow slow diffusion of HCl, afforded suitable single crystals for X-ray crystallographic studies. The compound crystallizes in the monoclinic space group P21/n. The flexible methylene phosphonic acid groups appended to both nitrogen termini adopt a trans configuration. The phosphonate and carbonyl groups (acceptors: P=O and C=O), together with water molecules [donor: O(6)—H∙∙∙O], participate in an extensive network of hydrogen-bonding interactions. Two of the phosphonate groups are protonated as P—OH (donors) and interact with oxygen atoms of neighboring phosphonate groups and water molecules. Hirshfeld surface analysis and associated two-dimensional fingerprint plots indicate that O∙∙∙H/H∙∙∙O (56.1%) contacts are the primary contributors to the crystal packing, followed by H∙∙∙H (16.3%) and C∙∙∙O/O∙∙∙C (13.4%) interactions. No significant π–π interactions were observed. The direct optical bandgap value, estimated from the Tauc plot, is 3.24 eV, indicating semiconducting behavior. The compound also exhibits thermal stability up to ~270 °C. These properties suggest that this compound may be a promising candidate for future investigation in organic electronic and optoelectronic materials.

Crystals doi: 10.3390/cryst16080505

Authors: Junxian Fang Jihong Wang Zichen Xue Yunyun Shi Youwei Tian Anlei Zhang

This study investigates the spatiotemporal evolution of nonlinear Thomson radiation from an electron driven by a tightly focused circularly polarized Gaussian laser pulse in the presence of a uniform externally applied magnetic field. The laser pulse width L is treated as the control parameter of independent simulations and is scanned with sufficiently fine resolution to identify dynamical transitions that may be obscured by sparse parameter sampling. The temporal radiation sequence, electron dynamics, optimal radiation direction, and full angular distribution are analyzed within a unified framework. The results reveal that the maximum radiated power per unit solid angle exhibits a distinct plateau–transition–plateau evolution rather than a smooth dependence on pulse width. Comparisons with percentile-based, time-averaged, and time-integrated radiation quantities confirm that this step effect is not solely an artifact of global maximization, but originates from the intermittent preservation and renewal of record radiation peaks. The strongest radiation events are governed by the combined contributions of the acceleration-dependent numerator and the high-order directional factor ξ−6, with the latter providing the dominant amplification of favorable emission geometries. As L increases, the optimal radiation polar angle shifts toward smaller values, indicating enhanced collimation, while the full angular radiation structure exhibits continuous azimuthal rotation and hierarchical relay activation from larger to smaller polar angles. These results establish a coherent physical picture of the spatiotemporal evolution of nonlinear Thomson radiation as a function of laser pulse width and provide source-side guidance for controlling compact high-frequency radiation with potential relevance to X-ray diffraction, scattering, and the high-resolution characterization of crystalline materials.

Crystals doi: 10.3390/cryst16080504

Authors: Peng Su Siyuan Tang Liangcan Fu Xinxin Yang Lijun Liu

This study employs density functional theory and quantum chemical calculations to investigate the gas-phase nucleation and growth mechanisms during chemical vapor deposition of silicon carbide. Based on thermodynamic stability evaluations of large clusters under various configurations, the lowest-energy ground-state structure was determined. The Gibbs free energy (ΔG) calculations of pure silicon clusters (Sin), single-carbon silicon clusters (SinC), and double-carbon silicon clusters (SinC2) were conducted at different temperatures. The findings reveal that silicon atoms promote cluster growth. The special 2D-to-3D configurational transition attenuates the reaction’s spontaneity. During the initial nucleation stage, the system tends to form SinC; however, as the size increases, it evolves into the more stable SinC2. This study reveals gas-phase cluster formation at the atomic scale, providing a theoretical foundation for suppressing detrimental gas-phase nucleation.

Crystals doi: 10.3390/cryst16080503

Authors: Xin Wang Cuirong Liu Yan Li Yulan Feng Yuhui Duan Zhisheng Wu

In order to verify the reliability and engineering applicability of the AE-CMT welding technology for magnesium alloy joining, AE-CMT welding experiments were conducted at welding speeds ranging from 0.5 to 3.0 m/min on 1.5 mm-thick H24-temper AZ31B magnesium alloy sheets using imported 1.2 mm-diameter WE-33M welding wire. Within the welding speed range of 0.5–3.0 m/min, increasing the welding speed progressively reduces heat input, thereby refining grains and homogenizing the microstructure. The welding heat input of the AE-CMT process ranges from 0.47 KJ/mm to 1.07 KJ/mm, and the grain sizes of the weld zone and HAZ are 9.61–14.18 μm and 6.35–12.22 μm, respectively. In the range of 0.5–2.0 m/min welding speed, increasing welding speed progressively enhances the tensile strength of the welded joint. Notably, joints fabricated at a welding speed of 2.0 m/min deliver the maximum tensile strength, equivalent to 98.0% of the base metal. Well-defined dimples are also detected on the corresponding fracture surfaces. A further increase in welding speed leads to a gradual reduction in the tensile strength of the welded joint. It is demonstrated that welding speed acts as a critical process parameter for tailoring the microstructure and mechanical properties of AE-CMT-welded AZ31B magnesium alloy joints.

Crystals doi: 10.3390/cryst16080502

Authors: Yixin Sun Jie Zhang Hai Gu Zulei Liang Jianhua Sun Jie Jiang Guoqing Dai Bin Li Zhonggang Sun

Al-Li alloys present significant challenges for conventional fusion-based additive manufacturing (AM) due to their low evaporation temperature and high reactivity with oxygen. As a solid-state process, friction stir additive manufacturing (FSAM) is expected to eliminate melting and solidification during processing, thereby overcoming these limitations. This study investigates the FSAM of 2195 Al-Li alloy through temperature measurements and numerical simulations. The research focuses on the temperature at the center of the deposited region and the phase evolution before and after FSAM. The results indicate that during FSAM, the temperature at the center of the deposited zone ranges from 458 to 497 °C. In terms of phase constitution, the T3-tempered alloy primarily consists of an α-Al matrix and the δ’ (Al3Li) phase. The T8-tempered alloy contains α-Al, θ’ (Al2Cu), and T1 (Al2CuLi) phases. In the nugget zone (NZ), the peak temperature exceeds 450 °C. As a result, the T1 and θ’ phases dissolve, leaving only a small amount of δ’/β’ precipitates. This study presents a preliminary investigation based on a single-layer FSAM process. These findings provide a foundation for optimizing FSAM process parameters for Al-Li alloys.

Crystals doi: 10.3390/cryst16080501

Authors: Mingxiang Liu Shizheng Li Bei Cai Song Liu

The grain size and texture of high-purity Cu-Al alloy are crucial for its application in sputtering targets. In order to improve the grain size and texture of high-purity Cu-Al alloy, clock rolling followed by a subsequent annealing process was employed in the study. In comparison with unidirectional rolling (UR), the grain structure and texture evolution during clock rolling and annealing were characterized and analyzed. The results show that clock rolling (CR) promotes the uniform distribution of strain, and produces a dominant Cube texture after rolling. Experiments have confirmed that CR is more conducive to the occurrence of recrystallization than UR. After recrystallization, a large amount of the S texture is present in the specimens of UR, while S texture is obviously weakened in the specimens of CR. In addition, Cube texture transforms to S and Copper textures during recrystallization in CR specimens. Overall, clock rolling helps to generate equiaxed grains and weaken the texture.

Crystals doi: 10.3390/cryst16080500

Authors: Alessandro Dell’Era Daniela Ariaudo Maria Di Pea Antonio Rinaldi Rodolfo Araneo Giovanni Battista Appetecchi

Sodium-ion batteries (NIBs) represent a promising alternative to lithium-ion technology due to the greater abundance and sustainability of sodium. However, the choice of suitable electrolytes is a major limiting factor for performance, safety, and operational life. Conventional organic electrolytes provide high ionic conductivity but suffer from flammability, volatility, and limited thermal stability. In this context, ionic liquids (ILs) emerge as promising alternatives due to their very or extremely high flame-retardant properties, very low vapor pressure, good to high power solvent, and wide electrochemical/thermal window. Despite these advantages, the use of ionic liquids in NIBs is hampered by their high intrinsic viscosity due to strong ion interactions. These characteristic limits the mobility of Na+ cations and reduces ionic conductivity, especially in low-temperature conditions, resulting in increased internal resistance and worsened performance at high current rates. To overcome these limitations, different strategies have been proposed based on the target selection of cation/anion pairs, the use of additives, and blending with low-content organic compounds, as well as the optimization of the electrolyte-electrode interface. Thus, the intent of authors in this review is to highlight the progress performed in the last decade, trying to realize a coherent and linear discussion on strategies in the use of ionic liquids for sodium-ion batteries.

Crystals doi: 10.3390/cryst16080499

Authors: Humaira Rizwana Mujeeb Khan Horiah A. Aldehaish Syed Farooq Adil Mohammed Rafi Shaik Mohamed E. Assal Mohammad Rafe Hatshan Mohammed Rafiq H. Siddiqui

In the original publication [...]

Crystals doi: 10.3390/cryst16080498

Authors: Yupeng Wang Zhuangchao Zhan Huilin Zhang Hongbo Qin Jiaqiang Huang Wangyun Li Caihang Liang Lili Wang Chengxu Lin Mingzhen Hu

To investigate the effects of trace phosphorus (P) addition on the solidification behavior, microstructure, and local mechanical response of β-Sn alloys, Sn–P alloys containing 0.02, 0.05, and 0.08 wt.% P were prepared. Phase constitution, solidification characteristics, and nanomechanical properties were characterized by X-ray diffraction, thermogravimetry–differential scanning calorimetry, and nanoindentation, respectively. Electron backscatter diffraction was additionally conducted on representative pure Sn and Sn–P0.08 samples to qualitatively compare the endpoint microstructures. All alloys were primarily composed of β-Sn, while localized P-rich secondary regions in Sn–P0.08 were indexed as Sn4P3. Trace P promoted heterogeneous nucleation and markedly modified solidification, increasing the solidification peak temperature by approximately 20–22 °C and reducing the undercooling from 39.83 °C to 17.50–20.33 °C. Relative to pure Sn, Sn–P0.08 exhibited more grain regions and grain boundaries, together with pronounced dendritic and locally refined features, indicating modified β-Sn nucleation and growth. Young’s modulus and hardness of Sn–P0.08 reached 29.86 GPa and 0.232 GPa, respectively. Inverse nanoindentation analysis revealed increased representative stress, strain-hardening exponent, and strength coefficient. Fracture-energy analysis showed superior crack-growth energy dissipation for Sn–P0.02, whereas Sn–P0.08 exhibited greater resistance to plastic deformation.

Crystals doi: 10.3390/cryst16080496

Authors: Gurudas Mandal Rahul Samanta Sandip Kunar Amitava Ghatak Habib Masum Aman Gupta Guojun Ma

In the aircraft industry, with the growing demand for advanced, sustainable structural materials, researchers are increasingly focusing on developing Al-Zn-Mg-Cu alloys, particularly the Al 7075 alloy with micro-alloying elements. However, load and environmental conditions pose problems for the aircraft industry by significantly reducing fleet service life. Thus, researchers are keen to use micro-alloying elements such as Ni, Ce, Ag, Sn, Ti, and Cd with the Al 7xxx base alloy to achieve enhanced mechanical properties, particularly hardness and tensile strength. Besides micro-alloying, the heat treatment (HT) process and cold working also have a favorable effect on the improvement of the mechanical properties. However, the addition of micro-alloying elements improves those properties more than HT and cold working processes. In this review study, several mechanical properties of the alloy have been comprehensively covered, which helps to establish a comparative analysis between the heat-treated base alloy and heat-treated micro-alloyed Al alloy. The base alloy, after micro-alloying, becomes enriched, with a high formability and workability, high conductivity, and good erosion protection that significantly make these alloys sustainable for the aircraft industry. The impact of dynamic changes accompanying the use of this lightweight alloy, after identifying the sensible necessities for the development of techniques, can effectively change the whole concept of the structural design. Hence, the key emphasis of the present review lies in a better understanding of the correlation between the structure and properties of micro-alloyed Al 7xxx alloy, which heralds a new era for aircraft industries.

Crystals doi: 10.3390/cryst16080497

Authors: Liyuan Zhang Chen Liang Chuanhui Gong

Two-dimensional (2D) antiferromagnets are highly promising for next-generation spintronics due to their ultrafast dynamics and robustness against stray fields; however, their practical application is severely hindered by the vanishing magneto-optic effects restricted by strict crystal symmetries. In this work, we propose a universal physical mechanism to activate and manipulate the magneto-optic Faraday effect in 2D fully compensated bilayer antiferromagnets using an external vertical electric field. By constructing a comprehensive tight-binding model and performing first-principles calculations on bilayer VSe2, we demonstrate that the applied electric field explicitly breaks the spatial inversion and combined PT symmetries. This symmetry breaking lifts the Kramers degeneracy, inducing a pronounced spin splitting that, in conjunction with intrinsic spin–orbit coupling, generates non-vanishing Berry curvature. Consequently, the previously forbidden Faraday rotation angle is activated from zero to a significant non-zero value, and its rotation direction can be deterministically reversed by switching the electric field polarity. Our findings provide profound physical insights into the symmetry-modulated light–matter interactions and pave the way for designing fully electrically controllable, energy-efficient antiferromagnetic opto-spintronic devices.

Crystals doi: 10.3390/cryst16080495

Authors: Lie Tian Rong Wu HaiYang Liu Dong Zhang Xiangqian Shen

Organic pollutant degradation demands photocatalysts that couple efficient charge separation with strong redox capability. Direct Z-scheme heterojunction architectures fulfill these requirements and are consequently considered promising candidates. However, the rational design of such systems continues to present a major obstacle. Herein, a CdSe/amorphous MoSex (CdSe/a-MoSex) direct Z-scheme heterojunction was successfully synthesized via a simple solid-state grinding and low-temperature hydrothermal method. Within 120 min under visible-light irradiation, methylene blue (MB, 40 mg/L) was degraded to 97.3% efficiency by the CdSe/a-MoSex heterojunction, whose photocatalytic activity markedly exceeded that of pristine CdSe and a-MoSex. Intimate interfacial contact between CdSe and a-MoSex enables photogenerated carriers to separate and migrate more efficiently, underpinning the observed performance enhancement. Moreover, the suitable band alignment derived from valence-band (VB) XPS and Mott-Schottky measurements supports the formation of a direct Z-scheme charge-transfer pathway. The Z-scheme mechanism effectively inhibits electron-hole recombination while maintaining the robust oxidation and reduction capabilities of the photogenerated carriers. This study offers a straightforward approach for fabricating CdSe/a-MoSex direct Z-scheme heterojunctions for the efficient photocatalytic degradation of organic pollutants.

Crystals doi: 10.3390/cryst16080494

Authors: Ethem Furkan Hıdır Ali Sincar Cevher Kürşat Macit Samet Tekin Ukbe Usame Uçar

Poly(methyl methacrylate) (PMMA) remains a clinically important denture base polymer because of its favorable processability, aesthetics, repairability and long-term prosthodontic use; however, its limited surface hardness and susceptibility to sliding-induced degradation constrain surface durability. This study establishes the structure–chemistry–microstructure–tribology relationships and composition-window predictive behavior of heat-polymerized PMMA reinforced with titanium diboride (TiB2). PMMA/TiB2 composites containing 1, 3 and 5 wt.% TiB2 were prepared and compared with unreinforced PMMA. X-ray diffraction confirmed preservation of the broad amorphous/semi-amorphous PMMA response, while TiB2-related crystalline features became increasingly detectable with reinforcement content. ATR-FTIR showed retention of the characteristic C–H, ester C=O and C–O/C–O–C vibrations. SEM/EDS demonstrated progressively greater particle-related surface contrast and local Ti/B-associated elemental signatures. Vickers microhardness increased from 20.0 ± 0.7 to 35.0 ± 1.39 HV0.03, corresponding to a 75.0% improvement at 5 wt.% TiB2. After 1000 m of dry sliding, total mass loss decreased from 32.4 ± 0.5 to 14.9 ± 0.4 mg (54.0% reduction), overall coefficient of friction decreased from 0.58 to 0.35, and representative wear-track width decreased from 481.4 to 101.8 µm. A parsimonious distance–composition interaction model retained strong grouped leave-one-composition-out performance for cumulative wear (R2 = 0.9622; RMSE = 1.53 mg), while a linear composition model provided the most robust hardness prediction (R2 = 0.9317; RMSE = 1.50 HV0.03). More complex nonlinear models did not improve prediction for held-out compositions. Within the investigated 0–5 wt.% window, 5 wt.% TiB2 provided the most effective combination of matrix preservation, surface hardening, wear suppression and frictional stabilization.

Crystals doi: 10.3390/cryst16080492

Authors: Kristen Oberle Daron E. Janzen

Polymorphic behavior has significant consequences in solid-state properties relevant to functional materials and pharmaceutical applications. This study reports the single-crystal X-ray structure of a new third unique polymorph of the photoluminescent compound [Cu(dmp)2](BF4) (dmp = 2,9-dimethyl-1,10-phenanthroline). A detailed analysis of how this new polymorph compares with the two previously reported polymorphs was carried out including intramolecular metrics (τ4, twisting, flattening, rocking measures) and intermolecular differences (π-stacking, Hirshfeld surfaces). The new polymorph reported here has larger twisting and flattening distortions from an idealized tetrahedral geometry and the largest displacement of Cu from one dmp plane than the other polymorphs. This new polymorph also exhibits enhanced π-stacking that leads to more dense packing than previous reported polymorphs. Hirshfeld surface comparisons are consistent with a larger percentage of C…C short contacts and lower percentage of C…H contacts present in this new polymorph. The variability of intra- and intermolecular differences within this family of three polymorphs compared demonstrates the large degree of flexibility of both the coordination sphere and packing, even with the expected rigid planar bis-bidentate dmp binding to copper. As the polymorphs each show unique inter- and intramolecular features, differences in solid-state properties including solid-state photoluminescence are expected. This demonstrates the importance of phase purity in the construction of solid-state device applications.

Crystals doi: 10.3390/cryst16080493

Authors: Shenggang Wang Chang Yu Lin Yang Xiaohong Yang

In this study, amorphous Cu86P7.5Sn4.5Ni2(wt.%) fillers were prepared using the melt spinning method with different rolling speeds. The wetting performance of these fillers on copper was assessed under different temperatures and holding times. The results indicated that the fillers obtained through the melt spinning technique exhibited lower melting temperatures than the as-cast filler. When processed at a rolling speed of 20 m/s, the amorphization of the filler was not sufficient. The higher rolling speed promoted the formation of the amorphous structure. The amorphous filler produced at 30 m/s exhibited the narrowest melting range and the lowest liquidus temperature (622 °C), which is approximately 100 °C lower than that of the as-cast filler (725 °C). Furthermore, the amorphous fillers also exhibited better wettability toward copper under the same conditions. Notably, the amorphous filler fabricated at 30 m/s demonstrated superior wettability at 750 °C for 90 s. Owing to the optimal wettability of the amorphized filler toward copper and the lower liquid temperature, the brazed copper joint achieved a shear strength of 223.2 MPa. The fracture of the four joints occurred in the base metal. In this study, we explored the brazing performance of amorphized Cu-based fillers, facilitating the solid bonding of copper at lower brazing temperatures.

Crystals doi: 10.3390/cryst16080491

Authors: Sara Lazghed Farida Annane Akila Boumaza Hocine Meradji Sebti Ghemid

In this work, the structural, mechanical, electronic, and optical properties of the 18-valence-electron half-Heusler compounds MCoBi (M = Ti, Zr, Hf) are investigated using the all-electron full-potential linearized augmented plane wave (FP-LAPW) method. The relativistic effect of spin–orbit coupling (SOC) is systematically incorporated and analyzed. Structural optimization confirms the stability of the Type-III phase, with lattice parameters in good agreement with available experimental data. Mechanically, the inclusion of SOC reduces both stiffness and brittleness, indicating a clear softening effect on the material behavior. SOC significantly lifts the degeneracy of the electronic bands, resulting in splitting (ΔSO) at the valence band maximum of approximately 0.10 eV and 0.12 eV for TiCoBi and ZrCoBi, respectively, which subsequently reduces the band gap; however, HfCoBi exhibits a remarkably weak splitting. The impact of SOC is further evidenced in the optical response across all three compounds. The absorption coefficient reaches high values (>105 cm−1) in the visible spectrum. Furthermore, a dramatic reduction in the intensity of plasmon resonance frequencies is observed, with values dropping to approximately 0.10–0.11 for the studied compounds. These findings highlight the potential of these materials for future electronic and optoelectronic device applications.

Crystals doi: 10.3390/cryst16080490

Authors: Alotaibi Fawaz Marzouq S Usman Ali Atta-Ur-Rehman Talal Ameen Ali Alhemyari

This study investigates the microstructural evolution and mechanical behavior of a Ni-based superalloy subjected to combined heat treatment and laser processing. Quantitative analysis of γ′ Ni3(Al,Ti) and η (Ni3Ti) phase distributions were performed using SEM-based statistical methods. The results show that γ′ precipitates exhibit a fine and uniform distribution with sizes in the range of ~0.05–0.30 µm and a high number density (n ≈ 2916), whereas the η (Ni3Ti) phase appears as relatively coarse particles (~0.1–0.6 µm) with lower number density (n ≈ 505). Laser treatment promotes redistribution of γ′ precipitates and suppresses η phase formation, resulting in improved microstructural homogeneity. Mechanical characterization reveals that optimal aging (2 h) yields the highest hardness of ~525 HV at 300 °C, while tensile properties show yield strength in the range of ~1000–1150 MPa and ultimate tensile strength of ~1300–1500 MPa. The results demonstrate a strong correlation between γ′ refinement and enhanced mechanical performance. These findings provide a quantitative understanding of phase evolution and establish a microstructure-property relationship for optimizing Ni-based superalloys.