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Crystallization of Four Troglitazone Isomers: Selectivity and Structural Considerations
Design of Near-UV Photoluminescent Liquid-Crystalline Dimers: Roles of Fluorinated Aromatic Ring Position and Flexible Linker
Structural Analysis of PlyKp104, a Novel Phage Endoysin

Journal Description

Crystals

Crystals is an international, peer-reviewed, open access journal on Crystallography published monthly online by MDPI. The Professional Committee of Key Materials and Technology for Electronic Components (PC-KMTEC) is affiliated with Crystals and its members receive discounts on the article processing charges.

Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, Ei Compendex, CAPlus / SciFinder, and other databases.
Journal Rank: JCR - Q2 (Crystallography) / CiteScore - Q2 (Condensed Matter Physics)
Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 12.7 days after submission; acceptance to publication is undertaken in 2.6 days (median values for papers published in this journal in the first half of 2025).
Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.

Impact Factor: 2.4 (2024); 5-Year Impact Factor: 2.4 (2024)

Imprint Information Journal Flyer Open Access ISSN: 2073-4352

Latest Articles

19 pages, 3894 KB

Open AccessFeature PaperReview

The Crystallography of Enzymes: A Retrospective and Beyond

by Tianyi Huang, Jannat Khan, Sheryar Lakhani, Albert Li, Aditya Vyas, Julia Hunt, Sara Andrea Espinosa Garcia and Bo Liang

Crystals 2025, 15(11), 966; https://doi.org/10.3390/cryst15110966 (registering DOI) - 8 Nov 2025

Crystallography plays a crucial role in understanding the functions of macromolecules by determining their three-dimensional structures at the atomic level. This review outlines the history of crystallization, explains the principles of crystallization, and provides a comprehensive retrospective on the role of crystallography in [...] Read more.

Crystallography plays a crucial role in understanding the functions of macromolecules by determining their three-dimensional structures at the atomic level. This review outlines the history of crystallization, explains the principles of crystallization, and provides a comprehensive retrospective on the role of crystallography in enzymology, with a particular focus on the seven Enzyme Commission (EC) classes. For each class, we highlight representative enzymes and the specific mechanistic insights enabled by crystal structures, oxidoreductases (the “yellow enzyme” lineage), transferases (phosphotransferase systems), hydrolases (RNase III and chymotrypsin), lyases (fumarase), isomerases (pseudouridine synthases), ligases (E3 ubiquitin ligases), and translocases (ATP synthase), emphasizing cofactor usage, conformational change, regulation, and implications for disease and drug discovery. We also compile EC-wide statistics from the Protein Data Bank (PDB) to quantify structural coverage. The limitations and challenges of current crystallization techniques are addressed, along with alternative experimental methods for structural elucidation. In addition, emerging computational tools and biomolecular design are also discussed. By reviewing the trajectory of enzymology and crystallography, we demonstrated their profound impact on biochemistry and therapeutic discovery. Full article

(This article belongs to the Special Issue Crystallography of Enzymes)

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7 pages, 1267 KB

Open AccessArticle

MOCVD Growth of Relaxed, Crack-Free AlGaN on Tiled GaN Substrates

by Nirupam Hatui, Henry Collins, Emmanuel Kayede, Feng Wu, Stacia Keller and Umesh K. Mishra

Crystals 2025, 15(11), 965; https://doi.org/10.3390/cryst15110965 (registering DOI) - 8 Nov 2025

Al_xGa_1-xN layers with up to 53% Al composition and 1.3 µm total thicknesses were grown utilizing step-graded layers on dense arrays of 10 × 10 µm² GaN tiles. While the layers were fully relaxed and crack-free, the higher [...] Read more.

Al_xGa_1-xN layers with up to 53% Al composition and 1.3 µm total thicknesses were grown utilizing step-graded layers on dense arrays of 10 × 10 µm² GaN tiles. While the layers were fully relaxed and crack-free, the higher Al composition sample showed increased X-ray line width, which did not correlate with a lack of increased dislocation density (as measured by TEM). Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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19 pages, 5457 KB

Open AccessArticle

High-Magnesium Olivines (Fo 90–100): Determination of Fo Content by Raman Spectroscopy

by Tianqi Wang, Mingyue He, Bijie Peng, Jingxuan Wang, Mei Yang and Ning Wang

Crystals 2025, 15(11), 964; https://doi.org/10.3390/cryst15110964 (registering DOI) - 7 Nov 2025

Olivine is a dominant constituent of the Earth’s upper mantle, and its forsterite content (Fo = 100 × Mg/(Mg + Fe_total) in molar basis) holds significant implications for indicating petrogenesis. The characteristic Raman doublet near ~820 and ~855 cm⁻¹ shifts [...] Read more.

Olivine is a dominant constituent of the Earth’s upper mantle, and its forsterite content (Fo = 100 × Mg/(Mg + Fe_total) in molar basis) holds significant implications for indicating petrogenesis. The characteristic Raman doublet near ~820 and ~855 cm⁻¹ shifts systematically to higher wavenumbers with increasing Fo content. Although previous studies have established general relationships between Fo content and Raman shifts in olivine, research focusing specifically on high-Fo (90–100) compositions remains limited, primarily due to a scarcity of suitable samples. This study addresses this gap by systematically investigating 45 high-Fo (90–100 olivine samples, to establish regression relationships between the Fo content and both the primary doublet (P1: 822–826 cm⁻¹; P2: 855–858 cm⁻¹) and three secondary peaks (P3: 881–884 cm⁻¹, P4: 917–921 cm⁻¹, and P5: 961–967 cm⁻¹). Our results show that, whereas the secondary peaks (P3–P5) show weak correlations with Fo values, the doublet exhibits a strong compositional dependence, providing a reliable basis for developing calibration models. To enable the rapid screening of unknown olivines, we established a generalized linear equation (Fo = −(3547 ± 65) + (4.25 ± 0.08) P2), with P2 > 855.0 cm⁻¹ indicating Fo > 90. For the precise quantification of these identified high-Fo samples, calibration models derived from the doublet show an excellent correlation with Fo (R² > 0.93), with residual fluctuation within ±2.5%, a leave-one-out cross-validation root-mean-square error (LOOCV-RMSE) of ~0.7. Notably, the quadratic regression model based on the P2 peak, Fo = (346,357 ± 10,890) − (812.4 ± 287.8) P2 + (0.477 ± 0.028) P2², demonstrates exceptional predictive stability and generalization capability, with prediction errors constrained within 4 Fo units. This model provides a reliable tool for the compositional discrimination for high-Fo olivine, enriches the Raman spectral database for olivine studies, and offers a robust method for the rapid and accurate compositional analysis of both terrestrial and extraterrestrial olivine samples. Full article

(This article belongs to the Section Mineralogical Crystallography and Biomineralization)

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15 pages, 4709 KB

Open AccessArticle

Low Coefficient of Thermal Expansion (CTE) Ceramic–Thermoplastic Composite for Fused Deposition Modelling of RF and Microwave Devices

by Vishvajitsinh Kosamiya, Liguan Li, Ioannis N. Gkikas, Juan D. Castro, Julia Oppenheimer, Ioannis Spanopoulos and Jing Wang

Crystals 2025, 15(11), 963; https://doi.org/10.3390/cryst15110963 - 7 Nov 2025

Additive manufacturing (AM) has significant potential for rapid prototyping of intricate 3-dimensional geometries, yet its adoption in RF and microwave applications remains limited. Key barriers include inadequate material characterization, high dielectric losses, poor thermal stability, and challenges with multi-material integration. This work addresses [...] Read more.

Additive manufacturing (AM) has significant potential for rapid prototyping of intricate 3-dimensional geometries, yet its adoption in RF and microwave applications remains limited. Key barriers include inadequate material characterization, high dielectric losses, poor thermal stability, and challenges with multi-material integration. This work addresses these issues by developing a high-k, low-loss composite filament with a reduced coefficient of thermal expansion (CTE), specifically formulated for fused deposition modelling (FDM). By varying filler volume fractions (30%, 40%, and 50% v/v) and surfactant content, their impact on thermal stability and CTE was investigated and measured by thermomechanical analysis (TMA). XRD, Pycnometry, and EDS analysis were performed to verify the effect of the calcination process on ceramic microfillers. The B.E.T. method (Brunauer–Emmet–Teller) was utilized to calculate the specific surface area of the samples with N₂ uptake. SEM images of the different composites were presented to visually demonstrate the homogeneous distribution of microfillers in the thermoplastic matrix. Titania was evaluated as the ceramic filler. Titania composites demonstrated decreased CTE values (35.93 ppm/°C at 50% v/v filler coated with surfactant) compared to composites without surfactant. A dielectric waveguide (DWG) printed with the T30S composite achieved an insertion loss of 0.46 dB at 17.23 GHz, significantly outperforming a commercially available ABS450-based DWG (0.95 dB at 16.88 GHz). Measurements aligned closely with 3D electromagnetic simulations, confirming dielectric properties (ε_r = 5.55, tan δ = 0.0009) suitable for advanced RF and microwave devices and advanced packaging applications. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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14 pages, 3891 KB

Open AccessArticle

Wavelength Conversion in Photonic Crystal Fibers via Multiple Raman Redshifts and Soliton Spectral Tunneling

by Mingliang Deng, Hui Wang and Bing Wen

Crystals 2025, 15(11), 962; https://doi.org/10.3390/cryst15110962 - 7 Nov 2025

The soliton spectral tunneling effect in photonic crystal fibers with three zero-dispersion wavelengths is an effective way to realize pulse wavelength conversion. However, due to the limitation of the soliton splitting mechanism, forming a tunneling soliton with larger energy and wider width by [...] Read more.

The soliton spectral tunneling effect in photonic crystal fibers with three zero-dispersion wavelengths is an effective way to realize pulse wavelength conversion. However, due to the limitation of the soliton splitting mechanism, forming a tunneling soliton with larger energy and wider width by increasing the number of Raman redshifts is still a key challenge. Airyprime pulses generate polychromatic Raman solitons with small truncation coefficients, and they converge into a stable soliton after the soliton tunneling effect, which provides a new possibility to solve this problem. This paper discusses how to control the energy, width and central wavelength characteristics of the tunneling solitons generated in the photonic crystal fiber with three zero-dispersion wavelengths by adjusting the truncation coefficient α, peak power P and central wavelength λ of the initial Airyprime pulse. The results show that the smaller the truncation coefficient α, the greater the number of Raman self-frequency shifts and the greater the energy of the formed tunneling soliton. The increase in initial power P₀ will lead to an increase in tunneling soliton width. The larger initial center wavelength λ will significantly increase the width and center wavelength position of the tunneling soliton. These findings provide a theoretical basis for the application of Airyprime pulses in ultrafast optical wavelength control and new light source development. Full article

(This article belongs to the Special Issue Metamaterials and Their Devices, Second Edition)

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17 pages, 17322 KB

Open AccessArticle

Effect of Annealing Process on Microstructure and Properties of Tin Bronze/Steel Bimetallic

by Zhangyong Yu and Chen Chen

Crystals 2025, 15(11), 961; https://doi.org/10.3390/cryst15110961 - 7 Nov 2025

Tin bronze/steel bimetallic is a widely utilized industrial material in the field of sliding bearing applications. Arc cladding technology represents an emerging method for fabricating tin bronze/steel bimetallic materials; however, research on their microstructure and mechanical properties remains limited. This study investigates the [...] Read more.

Tin bronze/steel bimetallic is a widely utilized industrial material in the field of sliding bearing applications. Arc cladding technology represents an emerging method for fabricating tin bronze/steel bimetallic materials; however, research on their microstructure and mechanical properties remains limited. This study investigates the microstructural characteristics and mechanical behavior of tin bronze/steel bimetallic materials produced via the arc cladding process, with particular emphasis on the effects of annealing treatment on these properties. The tin bronze layer consists of a fine-grained zone, a columnar dendritic zone, and a freely dendritic zone. The tin bronze/steel bimetallic material exhibits high mechanical strength and strong interfacial bonding. Nevertheless, during three-point bending tests, cracks are observed in the tin bronze layer. When annealed at temperatures ranging from 300 °C to 700 °C, the tensile strength, shear strength, and hardness of the material decrease, while the elongation increases significantly. Moreover, no cracking occurs during three-point bending tests. Upon reaching an annealing temperature of 800 °C, the overall mechanical performance deteriorates rapidly. An annealing temperature of 300 °C is identified as an optimal parameter for achieving favorable mechanical properties. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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13 pages, 3079 KB

Open AccessArticle

A Novel Energetic Nitroform Salt Derived from Bis-(Triazolyl)-Furoxan

by Fawei Wang, Jiapeng Wang, Zihu Wang, Jianhua Wang and Yucun Liu

Crystals 2025, 15(11), 960; https://doi.org/10.3390/cryst15110960 - 6 Nov 2025

This study presents the synthesis and comprehensive characterization of a novel nitroform salt, bis(2-methyl-3-amino-1,2,4-triazolyl)furoxan trinitromethanide (compound 2), derived from the molecular scaffold of bis-(2-methyl-3-amino-1,2,4-triazolyl)-furoxan (compound 1). The incorporation of the nitroform anion significantly enhances the energetic performance while maintaining moderate stability. [...] Read more.

This study presents the synthesis and comprehensive characterization of a novel nitroform salt, bis(2-methyl-3-amino-1,2,4-triazolyl)furoxan trinitromethanide (compound 2), derived from the molecular scaffold of bis-(2-methyl-3-amino-1,2,4-triazolyl)-furoxan (compound 1). The incorporation of the nitroform anion significantly enhances the energetic performance while maintaining moderate stability. Single-crystal X-ray diffraction analysis revealed that compound 2 crystallizes in the orthorhombic space group P2₁2₁2₁ with a density of 1.712 g·cm⁻³. Although its crystal packing adopts a less optimal zigzag-type mixed stacking mode and exhibits uneven electrostatic potential distribution, an extensive intramolecular hydrogen-bonding network contributes to its structural stability, as evidenced by a thermal decomposition temperature of 141 °C and impact sensitivity of 17 J. Detonation parameters calculated using EXPLO5 software demonstrate superior performance (detonation velocity = 8271 m·s⁻¹, detonation pressure = 26.9 GPa) compared to TNT and close proximity to RDX, coupled with markedly improved mechanical stability over both RDX and HMX. Hirshfeld surface and electrostatic potential analyses further elucidate the relationship between molecular structure and sensitivity, highlighting the critical role of hydrogen bonding in moderating mechanical sensitivity despite high energy content. These results underscore the potential of nitroform functionalization for designing advanced energetic materials with balanced performance and safety. Full article

(This article belongs to the Section Crystal Engineering)

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23 pages, 6717 KB

Open AccessArticle

Crystalline Nanoparticles and Their Impact on Electromagnetic Radiation Absorption in Advanced Clay Building Materials

by Jelena Brdarić Kosanović, Berislav Marković, Ivana Miličević, Anamarija Stanković and Dalibor Tatar

Crystals 2025, 15(11), 959; https://doi.org/10.3390/cryst15110959 - 6 Nov 2025

Given the increasing human exposure to electromagnetic radiation of various frequen-cies, mostly in the microwave range, awareness of potential health problems caused by this radiation has begun to grow. New building materials are being developed and tested to prevent or limit the penetration [...] Read more.

Given the increasing human exposure to electromagnetic radiation of various frequen-cies, mostly in the microwave range, awareness of potential health problems caused by this radiation has begun to grow. New building materials are being developed and tested to prevent or limit the penetration of microwave radiation, especially those frequencies that are used in mobile telephony. In contrast with the majority of the available literature on the investigation of concrete (cement) materials, in this paper, clay composite materials with the addition of nanoparticles of antimony(III)–tin(IV) oxide, zinc ferrite, iron(III) oxide, and two crystal modifications of titanium dioxide (rutile and anatase) were prepared in order to examine their effect on the absorption of electro-magnetic radiation. Nanomaterials are characterized by different physical and chemical methods. Specific surface area (B.E.T.), thermal properties (TGA/DSC), phase composition (PXRD), morphology (SEM), and chemical and mineralogical composition (EDX, and ED–XRF,) were determined. Thermal conductivity of clay composites was tested, and these materials showed a positive effect on the thermal conductivity (λ) of the composite: a reduction of 10–33%. The reflection and transmission coefficients of microwave radiation in the frequency range used in mobile telephony (1.5–4.0 GHz) were determined. From these data, the absolute value of radiation absorption in the materials was calculated. The results showed that the addition of the tested nanomaterials in a mass fraction of 3 to 5 wt.% significantly increases the absorption (reduces the penetration) of microwave radiation. Two nanomaterials, Sb₂O₃·SnO₂ and TiO₂ (rutile), have proven to be particularly effective: the reduction in transmission is 30–50%. The results of the test were correlated with the crystal structures of the examined nanomaterials. The inclusion of titanium dioxide and antimony-doped tin oxide into the clay led to a significant enhancement in microwave electromagnetic radiation absorption, which can be attributed to their interaction with the dielectric and conductive phases present in clay-based building materials. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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16 pages, 2329 KB

Open AccessArticle

Preparation of High-Purity Potassium Chloride Crystal Particles in an Octadecylamine Hydrochloride–Water System: The Correlation Between Morphology and Purity

by Yuchun Ren, Linjin Song, Mingyang Chen, Haitao Feng, Mingxuan Li and Jiaoyu Peng

Crystals 2025, 15(11), 958; https://doi.org/10.3390/cryst15110958 - 5 Nov 2025

In salt lake KCl cold decomposition–direct flotation for K-Na separation, octadecylamine hydrochloride (ODA-H) acts as a collector, reducing product purity and limiting high-end applications of salt lake KCl. To study KCl purification mechanisms and optimize crystal properties, this study investigates ODA-H aqueous systems. [...] Read more.

In salt lake KCl cold decomposition–direct flotation for K-Na separation, octadecylamine hydrochloride (ODA-H) acts as a collector, reducing product purity and limiting high-end applications of salt lake KCl. To study KCl purification mechanisms and optimize crystal properties, this study investigates ODA-H aqueous systems. By regulating the cooling rate, stirring rate, and ODA-H concentration, the crystallization purification of KCl and precise control of its morphology were achieved, ultimately yielding three typical crystal morphologies: cubic, spherical, and ellipsoidal. Of the three crystal morphologies, spherical crystals have the best flowability but lowest purity. Ellipsoidal crystals have better flowability than cubic ones: their purity exceeds that of cubic crystals before washing but falls below it after washing. Cubic crystals, with poorer flowability, reach the highest purity post-washing. This study provides a theoretical basis for enhancing purity via crystal morphology regulation and industrial-scale purification of salt lake KCl. Full article

(This article belongs to the Special Issue Crystallization Processes and Simulation Calculations, Fourth Edition)

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13 pages, 10495 KB

Open AccessArticle

Ligament-Size Effects on the Mechanical Behavior of Au/Cu Dual-Phase Spinodoid Nanocubes

by Jianjun Bian and Liang Yang

Crystals 2025, 15(11), 957; https://doi.org/10.3390/cryst15110957 - 5 Nov 2025

Spinodoid nanocubes, inspired by spinodal decomposition, feature bicontinuous dual-phase architectures with high interfacial area, offering a promising platform for tuning nanoscale mechanics. In the present study, classical molecular dynamics simulations are carried out to investigate the mechanical properties and deformation behaviors of Au/Cu [...] Read more.

Spinodoid nanocubes, inspired by spinodal decomposition, feature bicontinuous dual-phase architectures with high interfacial area, offering a promising platform for tuning nanoscale mechanics. In the present study, classical molecular dynamics simulations are carried out to investigate the mechanical properties and deformation behaviors of Au/Cu dual-phase spinodoid nanocubes. It is revealed that the ligament size of the spinodoid structure strongly influences material strength. As ligament size decreases, the strength of nanocubes increases until reaching a critical threshold, beyond which further refinement induces softening. This transition is governed by the semi-coherent interfaces through two competing mechanisms: for ligament sizes above the critical threshold, interfaces primarily impede dislocation motion, thereby strengthening the material; for smaller ligaments, interfacial plasticity, such as atomic rearrangements within the interface, provides a dominant softening mechanism. These findings highlight the critical role of characteristic length scale in determining the strength of nanocubes, and offer guidance for tailoring the mechanical performance of nanoscale dual-phase materials through structural design. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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18 pages, 2720 KB

Open AccessArticle

Influence of Nanocrystallite Size on Magnetic Properties of Iron Nitride γ’-Fe₄N

by Kamila Klimza, Grzegorz Leniec, Karol Synoradzki, Rafał Pelka, Urszula Nowosielecka, Izabela Moszyńska, Aleksander Guskos, Grzegorz Żołnierkiewicz and Nikos Guskos

Crystals 2025, 15(11), 956; https://doi.org/10.3390/cryst15110956 - 5 Nov 2025

In this paper, samples of nanocrystalline iron nitride γ’-Fe₄N, doped with small amounts of hardly reducible promoter oxides (Al₂O₃, CaO, and K₂O), were subjected to electron magnetic resonance (EMR) measurements. The samples differed in the [...] Read more.

In this paper, samples of nanocrystalline iron nitride γ’-Fe₄N, doped with small amounts of hardly reducible promoter oxides (Al₂O₃, CaO, and K₂O), were subjected to electron magnetic resonance (EMR) measurements. The samples differed in the average nanocrystallite size of iron nitride (23–54 nm). The EMR analysis was performed to probe the magnetic characteristics of the nanoparticles. The spectra, fitted with a Voigt function, were deconvoluted into contributions from the γ’-Fe₄N phase in the nanoparticle core and from surface-associated iron ions. The resulting magnetic responses were quantitatively correlated with nanoparticle size, elucidating finite-size effects governing the system’s magnetic behavior. Full article

(This article belongs to the Special Issue New Trends in Materials for Permanent Magnets)

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12 pages, 3226 KB

Open AccessArticle

Raman Spectral Analysis of Sputtered and Sulfurized Nanostructured WS₂ Films

by Magdaléna Kadlečíková, Ivan Hotový, Naman Kumar, Ivan Kostič, Michaela Sojková, Vlastimil Řeháček and Dagmar Gregušová

Crystals 2025, 15(11), 955; https://doi.org/10.3390/cryst15110955 - 5 Nov 2025

This study presents the Raman spectral characteristics and selected electrical parameter measurements of WS₂ films deposited by magnetron sputtering on sapphire and subsequently sulfurized. The analysis of the Raman spectra focuses on the positions and shifts of the E¹_2g and [...] Read more.

This study presents the Raman spectral characteristics and selected electrical parameter measurements of WS₂ films deposited by magnetron sputtering on sapphire and subsequently sulfurized. The analysis of the Raman spectra focuses on the positions and shifts of the E¹_2g and A_1g vibrational modes. The effects of different sputtering times on WS₂ films and the corresponding activation energy values were also investigated. From both physical and experimental perspectives, the Raman spectral features of WS₂ films were found to depend on the laser excitation wavelengths (532 nm and 632.8 nm) as well as on possible crystallographic defects and variations in the excitation point position. These defects have a significant influence on both the Raman spectra and the activation energies of the studied samples. The calculated activation energies (~ 0.15–0.19 eV) of the conduction charge carriers correlate with shallow defect-related energy levels indicated by the Raman characteristics. Full article

(This article belongs to the Section Crystal Engineering)

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15 pages, 8375 KB

Open AccessArticle

Femtosecond Laser-Processed, Copper-Coated Stainless Steel Implants Promoting In Situ Calcium Phosphate Crystallization for Orthopedic Application

by Albena Daskalova, Maja Dutour Sikirić, Liliya Angelova, Tihomir Car, Ana-Marija Milisav, Stuart Neil and Abeer Shaalan

Crystals 2025, 15(11), 954; https://doi.org/10.3390/cryst15110954 - 5 Nov 2025

Today, the engineering of load-bearing bone tissue after severe trauma still relies on metal-based (Ti, CoCrMo alloys or stainless steel) permanent implants. Such artificial scaffolds are typically applied in the body and come into direct contact with the recipient’s cells, whose adhesion affects [...] Read more.

Today, the engineering of load-bearing bone tissue after severe trauma still relies on metal-based (Ti, CoCrMo alloys or stainless steel) permanent implants. Such artificial scaffolds are typically applied in the body and come into direct contact with the recipient’s cells, whose adhesion affects the patient’s implant acceptance or rejection. The present study aims to create a nano-rough texture by means of ultra-short femtosecond laser (fs)-induced periodicity in the form of laser induced periodic surface structures (LIPSS) on the surface of a stainless steel implant model, which is additionally functionalized via magnetron-sputtering with a thin Cu layer, thus providing the as-created implants with a stable antimicrobial interface. Calcium phosphate (CaP) crystal growth was additionally applied due to the strong bioactive interface bond that CaPs provide to the bone connective tissue, as well as for the strong interface bond they create between the artificial implant and the surrounding bone tissue, thereby stabilizing the implanted structure within the body. The bioactive properties in the as-created antimicrobial hybrid topographical design, achieved through femtosecond laser-induced nanoscale surface structuring and micro-sized CaP crystal growth, have the potential for subsequent practical applications in bone tissue engineering. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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15 pages, 2298 KB

Open AccessArticle

Seed-Layer-Assisted Liquid-Phase Epitaxial Growth of YIG Films on Single-Crystal Yttrium Aluminum Garnet Substrates: Evidence for Enhancement in Strain-Induced Anisotropy

by Chaitrali Kshirsagar, Rao Bidthanapally, Ying Liu, Peng Zhou, Sahana Mukund, Aruna Bidthanapally, Hongwei Qu, Deepa Xavier, Subhabrat Samantaray, Venkatachalam Subramanian, Michael R. Page and Gopalan Srinivasan

Crystals 2025, 15(11), 953; https://doi.org/10.3390/cryst15110953 - 4 Nov 2025

Epitaxial thick films of yttrium iron garnet (YIG) are ideal for use in microwave devices due to their low losses at high frequencies. This report is on the growth of strain-engineered YIG films by liquid-phase epitaxy (LPE) on yttrium aluminum garnet (YAG) substrates [...] Read more.

Epitaxial thick films of yttrium iron garnet (YIG) are ideal for use in microwave devices due to their low losses at high frequencies. This report is on the growth of strain-engineered YIG films by liquid-phase epitaxy (LPE) on yttrium aluminum garnet (YAG) substrates with −3% lattice mismatch with YIG. Since the use of a lattice-matched substrate is preferred for LPE growths, a seed layer of YIG, 370–400 nm in thickness, was deposited by pulsed laser deposition (PLD) on (100), (110), and (111) YAG substrates. The seed layers were stoichiometric with magnetic parameters in agreement with the parameters for bulk single-crystal YIG and with strain-induced perpendicular magnetic anisotropy field H_a = 0.19–0.43 kOe. YIG films, 4 to 8.4 μm in thickness, were grown by LPE at 870 °C on YAG substrates with the seed layers using the PbO+B₂O₃ flux and annealed in air at 1000 °C. The films were Y-rich and Fe-deficient and confirmed to be epitaxial single crystals by X-ray diffraction. The saturation magnetization 4πM_s at room temperature was rather high and ranged from 1.9 kG to 2.3 kG. Ferromagnetic resonance at 5–15 GHz showed the absence of significant magneto-crystalline anisotropy in the LPE films with the line-width ΔH in the range 85–160 Oe, and H_a = 0.27–0.80 kOe which is much higher than for the seed layers. The high magnetization and H_a-values for the LPE films could be partially attributed to the off-stoichiometry. Although the strain due to the film–substrate lattice mismatch contributes to H_a, the mismatch in the thermal expansion coefficients for YIG and YAG is also a likely cause of H_a due to the high growth and annealing temperatures. The LPE-grown YIG films with high strain-induced anisotropy fields have the potential for use in self-biased microwave devices. Full article

(This article belongs to the Special Issue Single-Crystalline Composite Materials (Second Edition))

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17 pages, 3558 KB

Open AccessArticle

Single Crystal X-Ray Structure Determination and Vibrational Spectroscopy of 2-Aminopyrimidinium Hydrogen Trioxofluorophosphate and bis(2-Aminopyrimidinium) Trioxofluorophosphate

by Irena Matulková, Jan Fábry and Ivana Císařová

Crystals 2025, 15(11), 952; https://doi.org/10.3390/cryst15110952 - 3 Nov 2025

Two single-crystal X-ray structure determinations of 2-aminopyrimidinium hydrogen tri oxofluorophosphate, (C₄H₆N₃)⁺·(HFO₃P)⁻, (I), and bis(2-aminopyrimidinium) trioxofluorophosphate, 2(C₄H₆N₃)⁺·(FO₃P)²⁻, (II), as well [...] Read more.

Two single-crystal X-ray structure determinations of 2-aminopyrimidinium hydrogen tri oxofluorophosphate, (C₄H₆N₃)⁺·(HFO₃P)⁻, (I), and bis(2-aminopyrimidinium) trioxofluorophosphate, 2(C₄H₆N₃)⁺·(FO₃P)²⁻, (II), as well as their vibration spectra (FTIR on powder samples and the Raman spectra on unoriented single crystals) with a detailed assignment of vibrational modes are reported. The structure (I) consists of one independent 2-aminopyrimidinium cation and one hydrogen trioxofluorophosphate anion, while (II) consists of two symmetry independent 2-aminopyrimidinium cations and one trioxofluorophosphate anion. In (I), there is an O-H···O hydrogen bond of a moderate strength. A pair of these hydrogen bonds is situated about the symmetry centre and involved in the graph set motif R²₂(8). There are also N-H···O hydrogen bonds of a moderate strength, which are present in both structures while being involved in the graph set motifs R²₂(8), too. In addition, the N-H···O hydrogen bonds form R³₄(10) graph set motifs in (II). The latter motifs form ribbons which propagate parallel to the unit-cell axis a. In both structures, there are present π···π-electron ring interactions into which the primary amine groups are involved. In both structures, there are also present weak C-H···N hydrogen bonds with participation of the non-protonated ring N-atoms. The fluorine participates in the C-H···F hydrogen bonds in both title structures. The P-F distances are normal in both anions. The structure (I) differs from the known structure of 2-aminopyrimidinium hydrogen phosphite, the compositional isomer, though the main hydrogen bonds show similar geometry in both structures. The crystal of (I) was twinned. Full article

(This article belongs to the Section Organic Crystalline Materials)

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17 pages, 2210 KB

Open AccessArticle

The Preparation and Properties of Polycrystalline Bi₂O₂Se—Pitfalls in Reproducibility and Charge-Transport Limiting Factors

by Jan Zich, Tomáš Plecháček, Antonín Sojka, Petr Levinský, Jiří Navrátil, Pavlína Ruleová, Stanislav Šlang, Karel Knížek, Jiří Hejtmánek, Vojtěch Nečina and Čestmír Drašar

Crystals 2025, 15(11), 951; https://doi.org/10.3390/cryst15110951 - 3 Nov 2025

Thermoelectric materials enable the direct conversion of heat into electricity, but progress is often limited by challenges in reproducibility and stability. Bi₂O₂Se has recently attracted attention as a promising candidate; however, reported transport properties of undoped polycrystalline samples vary [...] Read more.

Thermoelectric materials enable the direct conversion of heat into electricity, but progress is often limited by challenges in reproducibility and stability. Bi₂O₂Se has recently attracted attention as a promising candidate; however, reported transport properties of undoped polycrystalline samples vary by several orders of magnitude, complicating its use as a baseline for doping studies. In this work, we investigate the sources of variability and identify key factors including precursor contamination, reactions with quartz ampoules and graphite dies, grain size effects, and surface oxidation. To mitigate these issues, we employed calcination of Bi₂O₃ precursors, synthesis with controlled temperature gradients, coarse-fraction powders, and hot pressing in Si₃N₄ dies. The resulting polycrystalline Bi₂O₂Se exhibits improved reproducibility, reduced sensitivity to thermal cycling, and characteristic transport values around σ_RT ≈ 500 S·m⁻¹ and S ≈ −300 μV·K⁻¹ at room temperature. This is a good starting point for further doping studies and a prerequisite of thermoelectric efficiency studies in the future, which can reveal the true thermoelectric potential of this material. Full article

(This article belongs to the Special Issue Research Progress on Thermoelectric Materials)

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23 pages, 9932 KB

Open AccessArticle

Explicit Crystal Plasticity Modeling of Texture Evolution in Nonlinear Twist Extrusion

by Ülke Şimşek, Hiroyuki Miyamoto and Tuncay Yalçınkaya

Crystals 2025, 15(11), 950; https://doi.org/10.3390/cryst15110950 - 2 Nov 2025

The Nonlinear Twist Extrusion (NLTE) method, a novel severe plastic deformation (SPD) technique, aims to enhance grain refinement and achieve a more uniform plastic strain distribution. Grain size and its uniform distribution strongly influence the physical properties of metals. Therefore, predicting texture evolution [...] Read more.

The Nonlinear Twist Extrusion (NLTE) method, a novel severe plastic deformation (SPD) technique, aims to enhance grain refinement and achieve a more uniform plastic strain distribution. Grain size and its uniform distribution strongly influence the physical properties of metals. Therefore, predicting texture evolution during processing is essential for optimizing forming parameters and improving material performance. In this study, a rate-dependent crystal plasticity formulation is implemented in an explicit framework in Abaqus finite element software, based on a finite strain approach with multiplicative decomposition of the deformation gradient. Crystal plasticity finite element (CPFEM) simulations are conducted on single-crystal copper under boundary conditions representing the NLTE process. The influence of dynamic friction coefficients on texture evolution is systematically investigated, and the results are compared with experimental observations. The study provides new insights into deformation mechanisms during NLTE and highlights the strong correlation between texture development and forming parameters. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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16 pages, 3646 KB

Open AccessArticle

Sintering of Alumina-Reinforced Ceramics Using Low-Temperature Sintering Additive

by Yuriy Alexandrovich Garanin, Rafael Iosifovich Shakirzyanov and Malik Erlanovich Kaliyekperov

Crystals 2025, 15(11), 949; https://doi.org/10.3390/cryst15110949 - 31 Oct 2025

Reinforced alumina ceramics are renowned for their high hardness and strength among common oxide ceramics. However, high-temperature or high-pressure treatment is necessary for maximizing values of strength and hardness. In this paper, liquid-phase-assisted pressureless sintering of alumina reinforced with zirconia was studied. Sintering [...] Read more.

Reinforced alumina ceramics are renowned for their high hardness and strength among common oxide ceramics. However, high-temperature or high-pressure treatment is necessary for maximizing values of strength and hardness. In this paper, liquid-phase-assisted pressureless sintering of alumina reinforced with zirconia was studied. Sintering of dense ceramic bodies in relatively low temperatures (up to 1100 °C) was possible with the usage of CuO-TiO₂-Nb₂O₅-based additive, together with an intense milling process. By using the XRD method, the formation of dominant α-Al₂O₃ and m-ZrO₂ phases with small concentrations of secondary ones in experimental samples was confirmed. SEM studies showed that uniform distribution of components in the composite was achieved in samples sintered from intensively milled powders. The significant increase in the values of Vickers hardness and biaxial flexural strength (by 2.6 times) in samples from intensively milled powders at a sintering temperature of 1050 °C was explained by reduced porosity, improved grain distribution, and the formation of the t-ZrO₂ phase in the alumina-reinforced composite. The study clearly showed high potential of the proposed low-temperature sintering method for zirconia-toughened aluminum oxide, which can be used in manufacturing of advanced ceramics. Full article

(This article belongs to the Special Issue Ceramic Materials: Structural, Mechanical and Dielectric Properties)

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11 pages, 2717 KB

Open AccessArticle

Precipitation of Fe-25Cr-5Al-Ti-RE Ferritic Stainless Steel Under Different Quenching Temperatures

by Xiaojian Du, Jianghua Ma, Guowang Song, Taotao Li, Jiayi Qi, Chengzhi Liu and Yucheng Yin

Crystals 2025, 15(11), 948; https://doi.org/10.3390/cryst15110948 - 31 Oct 2025

This study investigated the variation in precipitation in Fe-25Cr-5Al-Ti-RE ferritic stainless steel under different quenching heat treatment temperatures. Quenching heat treatments were performed at five temperatures, namely 600 °C, 700 °C, 800 °C, 900 °C, and 1000 °C. To analyze the alloy’s microstructure [...] Read more.

This study investigated the variation in precipitation in Fe-25Cr-5Al-Ti-RE ferritic stainless steel under different quenching heat treatment temperatures. Quenching heat treatments were performed at five temperatures, namely 600 °C, 700 °C, 800 °C, 900 °C, and 1000 °C. To analyze the alloy’s microstructure and precipitation behavior, comprehensive characterization techniques were employed, including X-ray Diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results demonstrated that after quenching at these temperatures, the main precipitation in the alloy was a chromium-rich phase (α′), aluminum oxide (Al₂O₃), titanium carbide (TiC), and titanium nitride (TiN). Specifically, Al₂O₃ was detected exclusively after heat treatments at 800 °C, 900 °C, and 1000 °C, with its particle size ranging from 10 nm to 100 nm. During high-temperature heat treatment, aluminum atoms and oxygen atoms in the matrix interacted with each other, and fine Al₂O₃ particles precipitated through a solid-state phase transition. Regarding titanium-containing precipitates, TiC precipitated after heat treatments at 700 °C, 800 °C, and 900 °C, whereas TiN was only observed after the quenching treatment at 1000 °C. The size of TiC particles fell within the range of 100 nm to 400 nm, while TiN particles exhibited a significantly larger size, spanning from 5 μm to 10 μm. Thermodynamic and kinetic analyses revealed that at elevated temperatures, nitrogen (N) exhibited a relatively high diffusion coefficient in the matrix; meanwhile, titanium (Ti) demonstrated an extremely strong chemical affinity for N. Consequently, even when the N content in the alloy was at a low level, N tended to preferentially react with Ti rather than with carbon (C) to form TiN. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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21 pages, 3272 KB

Open AccessArticle

Influence of Scanning Speed on the Electrochemical and Discharge Behavior of a CeO₂/Al6061 Anode for an Al–Air Battery Manufactured via Selective Laser Melting

by Shu Diao, Guanghong Zhou, Xiaobing Cao and Weipeng Duan

Crystals 2025, 15(11), 947; https://doi.org/10.3390/cryst15110947 - 31 Oct 2025

This study investigates how scanning speed influences the electrochemical performance and discharge behavior of aluminum–air (Al–air) batteries with CeO₂/Al6061 anodes fabricated through selective laser melting (SLM). Al–air batteries, celebrated for their exceptional energy density and eco-friendliness, encounter hurdles in their widespread [...] Read more.

This study investigates how scanning speed influences the electrochemical performance and discharge behavior of aluminum–air (Al–air) batteries with CeO₂/Al6061 anodes fabricated through selective laser melting (SLM). Al–air batteries, celebrated for their exceptional energy density and eco-friendliness, encounter hurdles in their widespread application due to anode self-corrosion and the formation of passivation films. To address these challenges, this study integrates CeO₂-reinforcing phases into Al6061 alloys and leverages SLM technology to enhance anode performance. A comprehensive analysis was conducted on the effects of varying scanning speeds (800, 900, 1000, 1100, and 1200 mm/s) on the surface morphology, density, self-corrosion rate, electrochemical performance, and discharge behavior of the anodes. The findings reveal that a scanning speed of 1000 mm/s produces anodes with optimal density, minimal self-corrosion, and outstanding electrochemical and discharge performance. Specifically, this scanning speed leads to a high discharge voltage of 1.575 V and an anode utilization rate of 72.2%, which can be attributed to the complete melting of the powder and the formation of a uniform microstructure. These insights offer valuable guidance for the development of high-performance Al–air batteries, promising extended lifespans and enhanced efficiency. Full article

(This article belongs to the Section Materials for Energy Applications)

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