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, 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 10.6 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the second half of 2023).
- 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:
2.7 (2022);
5-Year Impact Factor:
2.6 (2022)
Latest Articles
High Mechanical Property and Texture Degree of Hot−Extruded Bi0.905Sb0.095
Crystals 2024, 14(6), 557; https://doi.org/10.3390/cryst14060557 (registering DOI) - 16 Jun 2024
Abstract
Bi1−xSbx crystal is one of the best n−type thermoelectric materials below 200 K, but its weak mechanical strength hinders practical applications for deep refrigeration. Herein, we adopted the mechanical enhancement method of hot extrusion to investigate the comprehensive mechanical and
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Bi1−xSbx crystal is one of the best n−type thermoelectric materials below 200 K, but its weak mechanical strength hinders practical applications for deep refrigeration. Herein, we adopted the mechanical enhancement method of hot extrusion to investigate the comprehensive mechanical and thermoelectric properties of Bi0.905Sb0.095. It revealed that reducing the grain size of the matrix and increasing the extrusion ratio can improve the gain size uniformity and mechanical properties. Meanwhile, the thermoelectric performance depends on the texture, grain size, and local composition. The extruded sample prepared by ingot with the high extrusion ratio of 9:1 generated uniform small grains, which resulted in the high bending strength of Bi1−xSbx ~130 Mpa and a high power factor of ~68 μW·cm−1·K−2@173 K, as well as the relatively high figure of merit of 0.25@173K. This work highlights the importance of the uniform distribution of the grain size and the compositions for Bi1−xSbx, as well as the required universal key parameter for the hot extrusion method.
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(This article belongs to the Section Crystalline Metals and Alloys)
Open AccessArticle
Chloride-Induced Stress Corrosion Cracking of Friction Stir-Welded 304L Stainless Steel: Effect of Microstructure and Temperature
by
Anirban Naskar, Madhumanti Bhattacharyya, Saumyadeep Jana, Jens Darsell, Krishnan S. Raja and Indrajit Charit
Crystals 2024, 14(6), 556; https://doi.org/10.3390/cryst14060556 (registering DOI) - 16 Jun 2024
Abstract
Dry storage canisters of used nuclear fuels are fabricated using SUS 304L stainless steel. Chloride-induced stress corrosion cracking (CISCC) is one of the major failure modes of dry storage canisters. The cracked canisters can be repaired by friction stir welding (FSW), a low-heat
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Dry storage canisters of used nuclear fuels are fabricated using SUS 304L stainless steel. Chloride-induced stress corrosion cracking (CISCC) is one of the major failure modes of dry storage canisters. The cracked canisters can be repaired by friction stir welding (FSW), a low-heat input ‘solid-phase’ welding process. It is important to evaluate the ClSCC resistance of the friction stir welded material. Stress corrosion cracking (SCC) studies were carried out on mill-annealed base materials and friction stir welded 304L stainless U-bend specimens in 3.5% NaCl + 5 N H2SO4 solution at room temperature and boiling MgCl2 solution at 155 °C. The engineering stress on the outer fiber of the FSW U-bend specimen was ~60% higher than that of the base metal (BM). In spite of the higher stress level of the FSW, both materials (FSW and BM) showed almost similar SCC failure times in the two different test solutions. The SCC occurred in the thermo-mechanically affected zone (TMAZ) of the FSW specimens in the 3.5% NaCl + 5 N H2SO4 solution at room temperature, while the stirred zone (SZ) was relatively crack-free. The failure occurred at the stirred zone when tested in the boiling MgCl2 solution. Hydrogen reduction was the cathodic reaction in the boiling MgCl2 solution, which promoted hydrogen-assisted cracking of the heavily deformed stirred zone. The emergence of the slip step followed by passive film rupture and dissolution of the slip step could be the SCC events in the 3.5% NaCl + 5 N H2SO4 solution at room temperature. However, the slip step height was not sufficient to cause passivity breakdown in the fine-grained SZ. Therefore, the SCC occurred in the partially recrystallized softer TMAZ. Overall, the friction-stirred 304L showed higher tolerance to ClSCC than the 304L base metal.
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(This article belongs to the Section Crystalline Metals and Alloys)
Open AccessArticle
Synthesis, Structure and Magnetic Properties of Low-Dimensional Copper(II) trans-1,4-cyclohexanedicarboxylate
by
Pavel A. Demakov, Anna A. Ovchinnikova, Pavel V. Dorovatovskii, Vladimir A. Lazarenko, Alexander N. Lavrov, Danil N. Dybtsev and Vladimir P. Fedin
Crystals 2024, 14(6), 555; https://doi.org/10.3390/cryst14060555 (registering DOI) - 15 Jun 2024
Abstract
A reaction between copper(II) nitrate and trans-1,4-cyclohexanedicarboxylic acid (H2chdc) carried out under hydrothermal conditions led to a new metal-organic coordination polymer [Cu2(Hchdc)2(chdc)]n. According to single-crystal XRD data, the compound is based on bi-nuclear paddlewheel-type
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A reaction between copper(II) nitrate and trans-1,4-cyclohexanedicarboxylic acid (H2chdc) carried out under hydrothermal conditions led to a new metal-organic coordination polymer [Cu2(Hchdc)2(chdc)]n. According to single-crystal XRD data, the compound is based on bi-nuclear paddlewheel-type carboxylate blocks that are joined with polymeric chains due to the (μ3-κ1:κ2) coordination of carboxylate groups. The chains are interconnected by chdc2− bridging ligands into layers containing free COOH groups of terminal Hchdc−. The neighboring layers adopt a RCOOH···OOCR hydrogen bond-assisted arrangement into a dense-packed structure. Magnetization measurements showed the presence of a strong antiferromagnetic exchange interaction (J/kB = −495 K) inside the bi-nuclear blocks. At the same time, no significant interaction was found between the {-Cu2(OOCR)4-} units in spite of their polymeric in-chain packing. Patterns of magnetic behavior of [Cu2(Hchdc)2(chdc)]n were thoroughly analyzed and explained from a structural point of view.
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(This article belongs to the Section Hybrid and Composite Crystalline Materials)
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Superlattice Symmetries Reveal Electronic Topological Transition in CaC6 with Pressure
by
Bruce Wang, Antonio Bianconi, Ian D. R. Mackinnon and Jose A. Alarco
Crystals 2024, 14(6), 554; https://doi.org/10.3390/cryst14060554 - 14 Jun 2024
Abstract
The electronic properties of calcium-intercalated graphite (CaC6) as a function of pressure are revisited using density functional theory (DFT). The electronic band structures of CaC6, like many other layered superconducting materials, display cosine-shaped bands at or near the Fermi
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The electronic properties of calcium-intercalated graphite (CaC6) as a function of pressure are revisited using density functional theory (DFT). The electronic band structures of CaC6, like many other layered superconducting materials, display cosine-shaped bands at or near the Fermi level (FL). Such bands encompass bonding/antibonding information with a strong connection to superconducting properties. Using a hexagonal cell representation for CaC6, the construction of a double supercell in the c-direction effects six-folding in the reciprocal space of the full cosine function, explicitly revealing the bonding/antibonding relationship divide at the cosine midpoint. Similarly, folding of the Fermi surface (FS) reveals physical phenomena relevant to electronic topological transitions (ETTs) with the application of pressure. The ETT is characterised by a transition of open FS loops to closed loops as a function of pressure. As the highest transition temperature is reached with pressure, the dominant continuous, open FS loops shift to a different region of the FS. For CaC6, the peak value for the superconducting transition temperature, Tc, occurs at about 7.5 GPa, near the observed pressure of the calculated ETT. At this pressure, the radius of the nearly spherical Ca 4s-orbital FS coincides with three times the distance from the Γ centre point to the Brillouin zone (BZ) boundary of the 2c supercell. In addition, the ETT coincides with the alignment of the nonbonding (inflection) point of the cosine band with the FL. At other calculated pressure conditions, the Ca 4s-orbital FS undergoes topological changes that correspond and can be correlated with experimentally determined changes in Tc. The ETT is a key mechanism that circumscribes the known significant drop in Tc for CaC6 as a function of increasing pressure. Consistent calculated responses of the ETT to pressure match experimental measurements and validate the examination of superlattices as important criteria for understanding mechanisms driving superconductivity.
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(This article belongs to the Special Issue Computational and Theoretical Insights into Superconductors Advancements)
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Open AccessArticle
Study of Leakage Current Transport Mechanisms in Pseudo-Vertical GaN-on-Silicon Schottky Diode Grown by Localized Epitaxy
by
Mohammed El Amrani, Julien Buckley, Thomas Kaltsounis, David Plaza Arguello, Hala El Rammouz, Daniel Alquier and Matthew Charles
Crystals 2024, 14(6), 553; https://doi.org/10.3390/cryst14060553 - 14 Jun 2024
Abstract
In this work, a GaN-on-Si quasi-vertical Schottky diode was demonstrated on a locally grown n-GaN drift layer using Selective Area Growth (SAG). The diode achieved a current density of 2.5 kA/cm2, a specific on-resistance of
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In this work, a GaN-on-Si quasi-vertical Schottky diode was demonstrated on a locally grown n-GaN drift layer using Selective Area Growth (SAG). The diode achieved a current density of 2.5 kA/cm2, a specific on-resistance of 1.9 mΩ cm2 despite the current crowding effect in quasi-vertical structures, and an on/off current ratio (Ion/Ioff) of 1010. Temperature-dependent current–voltage characteristics were measured in the range of 313–433 K to investigate the mechanisms of leakage conduction in the device. At near-zero bias, thermionic emission (TE) was found to dominate. By increasing up to 10 V, electrons gained enough energy to excite into trap states, leading to the dominance of Frenkel–Poole emission (FPE). For a higher voltage range (−10 V to −40 V), the increased electric field facilitated the hopping of electrons along the continuum threading dislocations in the “bulk” GaN layers, and thus, variable range hopping became the main mechanism for the whole temperature range. This work provides an in-depth insight into the leakage conduction transport on pseudo-vertical GaN-on-Si Schottky barrier diodes (SBDs) grown by localized epitaxy.
Full article
(This article belongs to the Special Issue Wide Bandgap Semiconductor: GaN and SiC Material and Device)
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Open AccessReview
Recent Progress of Floating-Zone Techniques for Bulk Single-Crystal Growth
by
Naoki Kikugawa
Crystals 2024, 14(6), 552; https://doi.org/10.3390/cryst14060552 - 14 Jun 2024
Abstract
This review describes the recent progress of floating-zone techniques for bulk single-crystal growth. The most crucial point of the crucible-free technique is to keep the molten zone stable. It has been investigated and reported to yield a steeper temperature gradient at the liquid–solid
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This review describes the recent progress of floating-zone techniques for bulk single-crystal growth. The most crucial point of the crucible-free technique is to keep the molten zone stable. It has been investigated and reported to yield a steeper temperature gradient at the liquid–solid interface along the growth direction and a homogeneous molten liquid along the rotation axis. This article overviews several recent achievements starting from the conventional setup, particularly for lamps equipped in horizontal or vertical configurations, tilting mirrors, shielding the irradiation, and filament sizes for the optical-lamp floating-zone furnaces. Also, the recently advancing laser-heated floating-zone furnaces are described. Throughout the article, the author emphasizes that the floating-zone technique has been a powerful tool for crystal growth since the 1950s with its roots in the zone-melting method, and it has still been advancing for further materials’ growth such as quantum materials with modern scientific concepts.
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(This article belongs to the Special Issue Advances in Crystal Growth: Pioneering Materials for Tomorrow's Technologies)
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Abundant Catalytic Edge Sites in Few-Layer Horizontally Aligned MoS2 Nanosheets Grown by Space-Confined Chemical Vapor Deposition
by
Alin Velea, Angel-Theodor Buruiana, Claudia Mihai, Elena Matei, Teddy Tite and Florinel Sava
Crystals 2024, 14(6), 551; https://doi.org/10.3390/cryst14060551 - 14 Jun 2024
Abstract
Recently, a smart strategy for two-dimensional (2D) materials synthesis has emerged, namely space-confined chemical vapor deposition (CVD). Its extreme case is the microreactor method, in which the growth substrate is face-to-face stacked on the source substrate. In order to grow 2D transition metal
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Recently, a smart strategy for two-dimensional (2D) materials synthesis has emerged, namely space-confined chemical vapor deposition (CVD). Its extreme case is the microreactor method, in which the growth substrate is face-to-face stacked on the source substrate. In order to grow 2D transition metal dichalcogenides by this method, transition metal oxides, dispersed in very small amounts on the source substrate, are used as source materials in most of the published reports. In this paper, a colloidal dispersion of MoS2 in saline solution is used and MoS2 nanosheets with various shapes, sizes (between 5 and 60 μm) and thicknesses (2–4 layers) have been synthesized. Small MoS2 flakes (regular or defective) are present on the surface of the nanosheets. Catalytic sites, undercoordinated atoms located at the edges of MoS2 flakes and nanosheets, are produced in a high number by a layer-plus-island (Stranski–Krastanov) growth mechanism. Several double-resonance Raman bands (at 147, 177, 187, 225, 247, 375 cm−1) are assignable to single phonon processes in which the excited electron is elastically scattered on a defect. The narrow 247 cm−1 peak is identified as a topological defect-activated peak. These findings highlight the potential of defect engineering in material property optimization, particularly for solar water splitting applications.
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(This article belongs to the Special Issue Advanced Materials for Applications in Water Splitting)
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Unveiling the Synthesis of Strontium Ferrites by Sol-Gel and Laser Floating Zone Methods for Energy Application
by
Silvia Soreto Teixeira, Rafael Ferreira, João Carvalho and Nuno M. Ferreira
Crystals 2024, 14(6), 550; https://doi.org/10.3390/cryst14060550 - 13 Jun 2024
Abstract
This work proposes the synthesis of strontium ferrite by two different methods: sol-gel (SG), using powdered coconut water (PCW) as a precursor, and laser floating zone (LFZ). The SG samples were after treated at temperatures of 700, 1000, and 1200 °C, while the
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This work proposes the synthesis of strontium ferrite by two different methods: sol-gel (SG), using powdered coconut water (PCW) as a precursor, and laser floating zone (LFZ). The SG samples were after treated at temperatures of 700, 1000, and 1200 °C, while the samples obtained by LFZ were grown at pulling rates of 10, 50, and 100 mm/h. All samples studied were subjected to structural characterization techniques, as well as electrical (AC and DC) and magnetic characterization. Through X-ray diffraction, it was possible to observe that all the samples presented strontium ferrites, but none were single phase. The phases detected in XRD were confirmed by Raman spectroscopy. Scanning electron micrography allowed the observation of an increase in grain size with the temperature of SG samples and the reduction of the porosity with the decrease in growth rate for LFZ fibers. Through electrical analysis, it was observed that the most suitable samples for energy storage were the samples grown at 100 mm/h ( = 430,712; = 11,577; tan = 0.84; σac = 0.0006 S/m, at 1 kHz). The remaining samples had high dielectric losses and can be applied in electromagnetic shielding. The SG 700 °C sample presented the highest magnetization (38.5 emu/g at T = 5 K).
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(This article belongs to the Special Issue Advanced Research of Electroceramics for Energy Conversion, Storage and Devices)
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Open AccessArticle
The Temperature-Dependent Thermal Conductivity of C- and O-Doped Si3N4: First-Principles Calculations
by
Hongfei Shao, Jiahao Qiu, Xia Liu, Xuejun Hou and Jinyong Zhang
Crystals 2024, 14(6), 549; https://doi.org/10.3390/cryst14060549 - 13 Jun 2024
Abstract
Silicon nitride (Si3N4) possesses excellent mechanical properties and high thermal conductivity, which is an important feature in many applications. However, achieving the theoretically high thermal conductivity of Si3N4 in practice is challenging. In this study, we
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Silicon nitride (Si3N4) possesses excellent mechanical properties and high thermal conductivity, which is an important feature in many applications. However, achieving the theoretically high thermal conductivity of Si3N4 in practice is challenging. In this study, we adopted a first-principles calculation method to assess the effects of doping β-Si3N4 and γ-Si3N4 with carbon and oxygen atoms. Applying geometric structure optimization combined with calculation of the electronic phonon properties generated a stable doped structure. The results revealed that carbon and oxygen doping have little effect on the Si3N4 unit cell size, but that oxygen doping increases the unit cell volume. Energy band structure and state density calculation results showed that carbon doping reduces the nitride band gap width, whereas oxygen doping results in an n-type Si3N4 semiconductor. The findings from this study are significant in establishing a basis for targeted increase of the thermal conductivity of Si3N4.
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(This article belongs to the Section Materials for Energy Applications)
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Lactonization of α-Ferrocenyl Ketocarboxylic Acids via Nucleophilic Attack of Carbonyl Oxygen
by
Uttam R. Pokharel, Brennan J. Curole, Autumn M. Andras, Brandon P. LeBlanc and Frank R. Fronczek
Crystals 2024, 14(6), 548; https://doi.org/10.3390/cryst14060548 - 12 Jun 2024
Abstract
The effects of the ferrocenyl moiety to enhance the nucleophilicity of the carbonyl group, situated at its adjacent position, have been explored in a series of α-ferrocenyl ketocarboxylic acids. In the presence of trifluoroacetic anhydride, 3-ferrocenoylpropionic acid and 4-ferrocenoylbutyric acid gave 5-ferrocenyl-4-trifluoroacetyl-2(3H
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The effects of the ferrocenyl moiety to enhance the nucleophilicity of the carbonyl group, situated at its adjacent position, have been explored in a series of α-ferrocenyl ketocarboxylic acids. In the presence of trifluoroacetic anhydride, 3-ferrocenoylpropionic acid and 4-ferrocenoylbutyric acid gave 5-ferrocenyl-4-trifluoroacetyl-2(3H)-furanone and 6-ferrocenyl-5-trifluoroacetyl-3,4-dihydropyran-2-one, respectively. Under similar reaction conditions, 2-ferrocenylcarbonylbenzoic acid, a keto carboxylic acid without a β-hydrogen, gave a dimerized lactone, 3,3′-diferrocenyl-3,3′-diphthalide, possibly due to radical coupling. The nucleophilic attack of carbonyl oxygen, activated by the ferrocenyl moiety, on the carboxylic carbon is assumed to be the crucial mechanistic step in forming these lactones. When the carbonyl group was reduced to an alcohol to break its conjugation with the ferrocenyl moiety, saturated lactones were isolated after the acidic workup. These results indicate that the α-ferrocenyl carbinols readily undergo solvolysis under acidic conditions, giving ferrocenylcarbenium ions, which are attacked by the carboxy oxygen to give lactones.
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(This article belongs to the Special Issue Coordination Complexes: Synthesis, Characterization and Application)
Open AccessArticle
Investigations on the Carrier Mobility of Cs2NaFeCl6 Double Perovskites
by
Jiyuan Xing, Yiting Zhao, Wei-Yan Cong, Chengbo Guan, Zhongchen Wu, Dong Liu and Ying-Bo Lu
Crystals 2024, 14(6), 547; https://doi.org/10.3390/cryst14060547 - 12 Jun 2024
Abstract
Double perovskite materials have gradually become widely studied due to their potential applications in solar cells and other optoelectronic devices. We take Cs2NaFeCl6 as an example to investigate the carrier mobility with respect to the acoustic phonon and the optical
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Double perovskite materials have gradually become widely studied due to their potential applications in solar cells and other optoelectronic devices. We take Cs2NaFeCl6 as an example to investigate the carrier mobility with respect to the acoustic phonon and the optical phonon scattering mechanisms. By considering the deformation potential, carrier effective mass, and bulk modulus, the longitudinal acoustic (LA) phonon-determined mobilities for electrons and holes in Cs2NaFeCl6 are found to be μe = 2886.08 cm2 v−1 s−1 and μh = 39.09 cm2 v−1 s−1, respectively. The optical scattering mechanism involves calculating the Fröhlich coupling constant, dielectric constant, and polaron mass to determine the multiple polar optical (PO) phonon-scattering-determined mobilities, resulting in μe = 279.25 cm2 v−1 s−1 and μh = 21.29 cm2 v−1 s−1, respectively. By combining both interactions, the total electron mobility and hole mobility are determined to be 254.61 cm2 v−1 s−1 and 13.78 cm2 v−1 s−1, respectively. The findings suggest that the polarization of both electrons and ions, small coupling constant, and bulk modulus in Cs2NaFeCl6’s lattice make PO scattering a significant contribution to carrier mobility in this specific double perovskite, highlighting the importance of considering this in enhancing the optoelectronic properties of Cs2NaFeCl6 and other double perovskites.
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(This article belongs to the Section Inorganic Crystalline Materials)
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The Annealing Kinetics of Defects in CVD Diamond Irradiated by Xe Ions
by
Eugene A. Kotomin, Vladimir N. Kuzovkov, Aleksandr Lushchik, Anatoli I. Popov, Evgeni Shablonin, Theo Scherer and Evgeni Vasil’chenko
Crystals 2024, 14(6), 546; https://doi.org/10.3390/cryst14060546 - 12 Jun 2024
Abstract
The radiation-induced optical absorption at 1.5–5.5 eV (up to the beginning of fundamental absorption) has been analyzed in CVD diamond disks exposed to 231-MeV 132Xe ions with four fluences from 1012 to 3.8 × 1013 cm−2. The 5
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The radiation-induced optical absorption at 1.5–5.5 eV (up to the beginning of fundamental absorption) has been analyzed in CVD diamond disks exposed to 231-MeV 132Xe ions with four fluences from 1012 to 3.8 × 1013 cm−2. The 5 mm diameter samples (thickness 0.4 mm) were prepared by Diamond Materials, Freiburg (Germany); the average grain size at growth site was around 80 μm; and the range of xenon ions was R = 11.5 μm. The intensity of several bands grows with ion fluence, thus confirming the radiation-induced origin of the defects responsible for these bands. The recovery of radiation damage has been investigated via isochronal (stepwise) thermal annealing procedure up to 650 °C, while all spectra were measured at room temperature. Based on these spectra, the annealing kinetics of several defects, in particular carbon vacancies (GR1 centers with a broad band ~2 eV) and complementary C-interstitial-related defects (~4 eV), as well as impurity-related complex defects (narrow bands around 2.5 eV) have been constructed. The experimental kinetics have also been analyzed in terms of the diffusion-controlled bimolecular reactions. The migration energies of tentatively interstitial atoms (mobile components in recombination process) are obtained, and their dependence on the irradiation fluences is discussed.
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(This article belongs to the Section Materials for Energy Applications)
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Electro-Reactivity of Resorcinol on Pt(111) Single-Crystal Plane and Its Influence on the Kinetics of Underpotentially Deposited Hydrogen and Hydrogen Evolution Reaction Processes in 0.1 M NaOH Solution
by
Bogusław Pierożyński, Mateusz Kuczyński and Tomasz Mikołajczyk
Crystals 2024, 14(6), 545; https://doi.org/10.3390/cryst14060545 - 12 Jun 2024
Abstract
This article primarily presents cyclic voltammetry, Tafel polarization and ac. impedance spectroscopy electrochemical examinations of resorcinol (RC) electro-reactivity on the Pt(111) surface and its influence on the kinetics of UPD H (underpotentially deposited hydrogen) and the HER (hydrogen evolution reaction) in a
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This article primarily presents cyclic voltammetry, Tafel polarization and ac. impedance spectroscopy electrochemical examinations of resorcinol (RC) electro-reactivity on the Pt(111) surface and its influence on the kinetics of UPD H (underpotentially deposited hydrogen) and the HER (hydrogen evolution reaction) in a 0.1 M NaOH supporting solution. The collected data provided evidence of the RC-ion’s surface adsorption and its further electroreduction in the presence of surface-adsorbed H radicals along with their primary beneficial role on the kinetics of the UPD H process. The above was elucidated through an evaluation of the associated charge-transfer resistance and capacitance parameters, and was carried out on the platinum (111) electrode plane, comparatively, for the RC-free and resorcinol-modified NaOH electrolyte. In addition, the recorded cathodic charge transients (obtained by injecting small amounts of RC-based 0.1 M NaOH solution to initially resorcinol-free electrolyte, carried out at the constant electrode potential characteristic to the UPD H potential zone) provided evidence that the RC species undergoes electrocatalytic reduction through the involvement of the Pt(111)-chemisorbed hydrogen radicals.
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(This article belongs to the Special Issue Materials for Applications in Water Splitting and Battery)
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Open AccessEditorial
Self–Assembled Complexes: “Love at First Sight”
by
Ana M. García-Deibe and Jesús Sanmartín-Matalobos
Crystals 2024, 14(6), 544; https://doi.org/10.3390/cryst14060544 - 11 Jun 2024
Abstract
Self-assembly is a key process to obtain auto-organized species from disordered components [...]
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(This article belongs to the Special Issue Self-Assembled Complexes: “Love at First Sight”)
Open AccessEditorial
Recent Advances in Photonic Crystal and Optical Devices
by
Muhammad A. Butt and Svetlana N. Khonina
Crystals 2024, 14(6), 543; https://doi.org/10.3390/cryst14060543 - 11 Jun 2024
Abstract
In recent years, photonic crystals (PhCs) have garnered significant attention due to their extraordinary ability to control and manipulate light at the nanoscale [...]
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(This article belongs to the Special Issue Recent Advances in Photonic Crystal and Optical Devices)
Open AccessCorrection
Correction: Ghezzi, F.; Shmayda, W.T. Aging Effects in Zr(Fe0.5V0.5)2 Tritides. Crystals 2024, 14, 159
by
Francesco Ghezzi and Walter Theodore Shmayda
Crystals 2024, 14(6), 542; https://doi.org/10.3390/cryst14060542 - 11 Jun 2024
Abstract
There was an error in the original publication [...]
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(This article belongs to the Special Issue Hydrogen Embrittlement of Metals)
Open AccessArticle
Change in Growth Mode of BGaN Layers Grown on GaN
by
Jacek M. Baranowski, Kinga Kosciewicz, Ewelina B. Mozdzynska and Julita Smalc-Koziorowska
Crystals 2024, 14(6), 541; https://doi.org/10.3390/cryst14060541 - 11 Jun 2024
Abstract
A change in the growth mode from Stranski–Krastanov one, which is characteristic of MOCVD grown GaN, to the laterally grown BGaN in the Volmer–Weber growth mode is described. This change in growth is evidenced by scanning electron microscopy (SEM) and transmission electron microscopy
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A change in the growth mode from Stranski–Krastanov one, which is characteristic of MOCVD grown GaN, to the laterally grown BGaN in the Volmer–Weber growth mode is described. This change in growth is evidenced by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of BGaN grown on GaN at high temperatures. It is postulated on the basis of SIMS and XRD results that this change in growth is initiated by the transfer of boron atoms from gallium substitutional to interstitial. The proposed mechanism for the observed growth change is related to the generation of nitrogen interstitials and subsequent reactions with boron interstitials, which result in the formation of a BN layer at the growth front. The observed large change in the growth mode is due to a lattice mismatch between the grown BGaN and the atomic layer of BN and stays behind the change to the Volmer–Weber growth mode. The consequence of the Volmer–Weber growth mode is the textural layer of BGaN. The textural character of this material is associated with large voids between grown BGaN “plates”. These large voids are responsible for the termination of threading dislocations propagating in the c-direction. It is also postulated that the blocked threading dislocations from the GaN underlayer and laterally grown BGaN layers along the a-directions are responsible for the decrease in defect concentration within these layers.
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(This article belongs to the Special Issue Advanced Optoelectronic Crystals and Devices: Designing and Characterization)
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Multifunctional Experimental Studies of Sm-Ion-Influenced Pseudo-Cubic Morphotropic Phase Boundary Regional BiFeO3-xSrTiO3 Ceramics for High-Temperature Applications
by
Ahmad Hussain, Nawishta Jabeen, Aasma Tabassum, Muhammad Usman Khan, Laiba Basharat and Islam H. El Azab
Crystals 2024, 14(6), 540; https://doi.org/10.3390/cryst14060540 - 9 Jun 2024
Abstract
In this manuscript, for the first time, the exploration of the microstructural, ferroelectric, piezoelectric, and dielectric performances are measured for Sm-ion-influenced pseudo-cubic, morphotropic phase boundary (MPB) regional 0.62BiFeO3−0.38SrTiO3:xwt%Sm2O3 (BFST:xSm) ceramics with x = 0–0.25. All the
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In this manuscript, for the first time, the exploration of the microstructural, ferroelectric, piezoelectric, and dielectric performances are measured for Sm-ion-influenced pseudo-cubic, morphotropic phase boundary (MPB) regional 0.62BiFeO3−0.38SrTiO3:xwt%Sm2O3 (BFST:xSm) ceramics with x = 0–0.25. All the compositions maintained their pseudo-cubic MPB structural stability. The composition of BFST:0.15Sm ceramics exhibited an excellent remnant polarization (Pr) of ~52.11 μC/cm2, an enhanced d33 of 101 pC/N, and the highest relative dielectric constant (ɛr) of ~1152, which are much improved as compared to that of pure BFST ceramics. BFST:0.15Sm ceramics demonstrated a Curie temperature (TC) of 378 °C. Moreover, the composition exhibited high thermal stability for d33 72 pC/N (only a 28% decrease), even at a high temperature of 300 °C. Such outstanding outcomes make BFST:0.15Sm ceramics an ideal applicant for high-temperature piezoelectric applications.
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(This article belongs to the Section Polycrystalline Ceramics)
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The Wannier-Mott Exciton, Bound Exciton, and Optical Phonon Replicas of Single-Crystal GaSe
by
Long V. Le, Tran Thi Thu Huong, Tien-Thanh Nguyen, Xuan Au Nguyen, Thi Huong Nguyen, Sunglae Cho, Young Dong Kim and Tae Jung Kim
Crystals 2024, 14(6), 539; https://doi.org/10.3390/cryst14060539 - 8 Jun 2024
Abstract
We report the absorption and photoluminescence spectra of GaSe single crystals in the near-edge region. The temperatures explored the range from 17 to 300 K. Specifically, at a temperature of 17 K, the photoluminescence spectrum reveals an interesting phenomenon: the Wannier-Mott exciton separates
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We report the absorption and photoluminescence spectra of GaSe single crystals in the near-edge region. The temperatures explored the range from 17 to 300 K. Specifically, at a temperature of 17 K, the photoluminescence spectrum reveals an interesting phenomenon: the Wannier-Mott exciton separates into two states. These states are a triplet state with an energy of 2.103 eV and a singlet state with an energy of 2.109 eV. The energy difference between these two states is 6 meV. Furthermore, the bound exciton (BX) can be localized at an energy of 2.093 eV. It is worth noting that its phonon replicas (BX-nLO) can be clearly distinguished up to the fourth order. Interestingly, the energy gaps between these replicas exhibit a consistent spacing of 7 ± 0.5 meV. This intriguing finding suggests a high-quality crystalline structure as well as a strong coupling between the phonon and BX-nLO. Additionally, at low temperatures, both the ground state (n = 1) at 2.11 eV and the excited state (n = 2) at 2.127 eV of free excitons can be observed.
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(This article belongs to the Topic Optoelectronic Materials, 2nd Volume)
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Pressure-Driven Responses in Cd2SiO4 and Hg2GeO4 Minerals: A Comparative Study
by
Jaspreet Singh, Daniel Errandonea, Venkatakrishnan Kanchana and Ganapathy Vaitheeswaran
Crystals 2024, 14(6), 538; https://doi.org/10.3390/cryst14060538 - 7 Jun 2024
Abstract
The structural, elastic, and electronic properties of orthorhombic Cd2SiO4 and Hg2GeO4 were examined under varying pressure conditions using first-principles calculations based on density functional theory employing the Projector Augmented Wave method. The obtained cell parameters at 0
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The structural, elastic, and electronic properties of orthorhombic Cd2SiO4 and Hg2GeO4 were examined under varying pressure conditions using first-principles calculations based on density functional theory employing the Projector Augmented Wave method. The obtained cell parameters at 0 GPa were found to align well with existing experimental data. We delved into the pressure dependence of normalized lattice parameters and elastic constants. In Cd2SiO4, all lattice constants decreased as pressure increased, whereas, in Hg2GeO4, parameters a and b decreased while parameter c increased under pressure. Employing the Hill average method, we calculated the elastic moduli and Poisson’s ratio up to 10 GPa, noting an increase with pressure. Evaluation of ductility/brittleness under pressure indicated both compounds remained ductile throughout. We also estimated elastic anisotropy and Debye temperature under varying pressures. Cd2SiO4 and Hg2GeO4 were identified as indirect band gap insulators, with estimated band gaps of 3.34 eV and 2.09 eV, respectively. Interestingly, Cd2SiO4 exhibited a significant increase in band gap with increasing pressure, whereas the band gap of Hg2GeO4 decreased under pressure, revealing distinct structural and electronic responses despite their similar structures.
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(This article belongs to the Section Crystalline Metals and Alloys)
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