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Crystals, Volume 14, Issue 6 (June 2024) – 85 articles

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12 pages, 3985 KiB  
Article
Modelling and Control of Thermal Stress in TSLAG (Tb3Sc1.95Lu0.05Al3O12) Magneto-Optical Crystals Grown by Czochralski Method
by Junling Ding, Yu Zhang, Yuankai Hao and Xiuwei Fu
Crystals 2024, 14(6), 564; https://doi.org/10.3390/cryst14060564 (registering DOI) - 18 Jun 2024
Viewed by 70
Abstract
Tb3Sc1.95Lu0.05Al3O12 (TSLAG) crystals are novel and high-quality magneto-optical materials with the most promising application as the core component of Faraday devices. Cracking is an obstacle to TSLAG crystal growth and is closely influenced by [...] Read more.
Tb3Sc1.95Lu0.05Al3O12 (TSLAG) crystals are novel and high-quality magneto-optical materials with the most promising application as the core component of Faraday devices. Cracking is an obstacle to TSLAG crystal growth and is closely influenced by crystal thermal stress distribution. In this work, the evolution of thermal stress during TSLAG crystal growth in the initial Czochralski (Cz) furnace is numerically studied. The reasons for high thermal stress in TSLAG crystal are explained based on the results about the melt flow, the temperature distribution in the furnace, and the crystal/melt interface shape. A large crucible with a shallow melt is proposed to address the problem of significant variations in melt depth during TSLAG crystal growth. Based on the numerical results, the proposed design can stabilize the melt flow structure, suppressing changes in the crystal/melt interface shape and effectively improving thermal stress in the TSLAG crystal growth process, which contributes to precisely regulating the preparation of large-sized high-quality TSLAG crystals. Full article
(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Second Edition)
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9 pages, 1587 KiB  
Article
In Situ Calculation of the Rotation Barriers of the Methyl Groups of Tribromomesitylene Crystals: Theory Meets Experiment
by Anissa Amar, Soria Zeroual, Xavier Rocquefelte and Abdou Boucekkine
Crystals 2024, 14(6), 563; https://doi.org/10.3390/cryst14060563 - 18 Jun 2024
Viewed by 92
Abstract
The computation of the rotation barriers of the methyl groups (Me) of tribromomesitylene (TBM) crystals has been carried out. Experimentally, the barriers of the three Me groups of TBM are found to be high and different. These groups do not experience the same [...] Read more.
The computation of the rotation barriers of the methyl groups (Me) of tribromomesitylene (TBM) crystals has been carried out. Experimentally, the barriers of the three Me groups of TBM are found to be high and different. These groups do not experience the same hindering environment in the crystal state. For an isolated TBM molecule, the three barriers are equal and very low. We found that a cluster of 21 TBM molecules permits the reproduction of the crystal symmetry and structure of the bulk, with a central molecule surrounded by six molecules in the same plane and seven other molecules in two planes above and below. DFT computations including dispersion corrections have been carried out using the ONIOM procedure. The Me groups of the central TBM molecule were rotated step by step to determine the conformations of lowest and highest energy for each Me, thus allowing estimation of the rotation barriers as the difference between these energies. In doing so, we found the following barrier values, namely 105, 173, and 205 cm−1, whereas the experimental values were 111, 180 and 200 cm−1. Full article
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24 pages, 66534 KiB  
Article
Effect of Preparation Process on the Microstructure and Characteristics of TiAl Pre-Alloyed Powder Fabricated by Plasma Rotating Electrode Process
by Yu Zhang, Meihui Song, Yan Li, Yanchun Li, Shulin Gong and Bin Zhang
Crystals 2024, 14(6), 562; https://doi.org/10.3390/cryst14060562 - 18 Jun 2024
Viewed by 87
Abstract
TiAl pre-alloyed powder is the foundation for additive manufacturing of TiAl alloys. In this work, TiAl pre-alloyed powder was prepared using a plasma rotating electrode process (PREP). The effects of electrode rotating speeds and current intensity on the microstructure and characteristics of TiAl [...] Read more.
TiAl pre-alloyed powder is the foundation for additive manufacturing of TiAl alloys. In this work, TiAl pre-alloyed powder was prepared using a plasma rotating electrode process (PREP). The effects of electrode rotating speeds and current intensity on the microstructure and characteristics of TiAl pre-alloyed powder have been investigated in detail. The results show that the electrode rotating speeds mainly affected the average particle size of the powder (D50). As the electrode rotating speed increased, the D50 of the powder decreased. The current intensity mainly affected the particle size distribution of the powder. As the current intensity increased, the particle size distribution of the powder became narrower, which was concentrated at 45~105 μm. In addition, the current intensity had a significant effect on the sphericity degree of the powder with the particle size > 105 μm, but it had little effect on that <105 μm powder. TiAl pre-alloyed powder with a particle size > 45 μm demonstrated a dendritic + cellular structure, and the <45 μm powder had a microcrystalline structure. The powder was mainly composed of the α2 phase and γ phase. There were two kinds of phase structure inside the powder, namely the α2 + γ lamellar microstructure (particle size < 45 µm) and the α2 + γ network microstructure (particle size > 45 µm). The phase structure of the powder was related to the solidification path and cooling rate of molten droplets in the PREP. The average thickness of the α2 + γ lamellar was about 200 nm, in which the lamellar γ phases were arranged in an orderly manner in the α2 phase matrix with a thickness of about 20 nm. The network phase structure was corrugated, and the morphology of the γ phase was not obvious. Full article
(This article belongs to the Special Issue Progress in Light Alloys)
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19 pages, 10925 KiB  
Article
Optimization of Process Parameters and Microscopic Morphology of Multi-Walled Carbon Nanotubes/PEEK Films Using the Vacuum Suction Filtration Method
by Mingyu Liu, Hongya Fu, Songsong Yu, Ziang Jin, Zhenyu Han and Shouzheng Sun
Crystals 2024, 14(6), 561; https://doi.org/10.3390/cryst14060561 - 17 Jun 2024
Viewed by 197
Abstract
Multi-walled carbon nanotubes (MWCNTs) are a high-quality interlamination reinforcement material, but the high viscosity of polyetheretherketone (PEEK) prevents good fusion between MWCNTs and PEEK. This study proposes a method to achieve the complete integration of MWCNTs and PEEK through the preparation of a [...] Read more.
Multi-walled carbon nanotubes (MWCNTs) are a high-quality interlamination reinforcement material, but the high viscosity of polyetheretherketone (PEEK) prevents good fusion between MWCNTs and PEEK. This study proposes a method to achieve the complete integration of MWCNTs and PEEK through the preparation of a composite film using the vacuum suction filtration (VSF) method and optimizes the process parameters. An orthogonal experiment with three factors (filter paper pore size, ultrasonic dispersion time, and PEEK content) at three levels is designed, and mechanical performance testing and microscopic morphology observation are conducted. The influence of the three factors of filter paper pore size, ultrasonic time, and PEEK content on the elastic modulus and tensile strength of the film is investigated. The results are a filter paper pore size of 0.45 μm, ultrasonic time of 8.3 h, and PEEK content of 336.524 mg. The mechanical performance obtained under the optimal process parameters are an elastic modulus of 2437.5723 MPa and a tensile strength of 46.5196 MPa. This optimal process increases the elastic modulus by 12.3152% while maintaining a high tensile strength. Full article
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16 pages, 6322 KiB  
Article
X-ray Single-Crystal Analysis, Pharmaco-Toxicological Profile and Enoyl-ACP Reductase-Inhibiting Activity of Leading Sulfonyl Hydrazone Derivatives
by Yoanna Teneva, Rumyana Simeonova, Orlin Besarboliev, Hristina Sbirkova-Dimitrova and Violina T. Angelova
Crystals 2024, 14(6), 560; https://doi.org/10.3390/cryst14060560 - 17 Jun 2024
Viewed by 199
Abstract
Taking into consideration the growing resistance towards currently available antimycobacterials, there is still an unmet need for the development of new chemotherapeutic agents to combat the infectious agents. This study presents X-ray single-crystal analysis to verify the structure of leading sulfonyl hydrazone 3b [...] Read more.
Taking into consideration the growing resistance towards currently available antimycobacterials, there is still an unmet need for the development of new chemotherapeutic agents to combat the infectious agents. This study presents X-ray single-crystal analysis to verify the structure of leading sulfonyl hydrazone 3b, which has proven its potent antimycobacterial activity against Mycobacterium tuberculosis H37Rv with an MIC value of 0.0716 μM, respectively, low cytotoxicity, and very high selectivity indexes (SI = 2216), and which has been fully characterized by Nuclear Magnetic Resonance (NMR) and High-Resolution Mass Spectrometry (HRMS) methods. Furthermore, this study assessed the ex vivo antioxidant activity, acute and subacute toxicity, and in vitro inhibition capacity against enoyl-ACP reductase of hydrazones 3a and 3b, as 3a was identified as the second leading compound in our previous research. Compared to isoniazid, compounds 3a and 3b demonstrated lower acute toxicity for intraperitoneal administration, with LD50 values of 866 and 1224.7 mg/kg, respectively. Subacute toxicity tests, involving the repeated administration of a single dose of the test samples per day, revealed no significant deviations in hematological and biochemical parameters or pathomorphological tissues. The compounds exhibited potent antioxidant capabilities, reducing malondialdehyde (MDA) levels and increasing reduced glutathione (GSH). Enzyme inhibition assays of the sulfonyl hydrazones 3a and 3b with IC50 values of 18.2 µM and 10.7 µM, respectively, revealed that enoyl acyl carrier protein reductase (InhA) could be considered as their target enzyme to exhibit their antitubercular activities. In conclusion, the investigated sulfonyl hydrazones display promising drug-like properties and warrant further investigation. Full article
(This article belongs to the Section Organic Crystalline Materials)
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9 pages, 5570 KiB  
Article
Influence of Powder Size on Pore Characteristics and Intermetallic Phase Kinetics in Porous Ti-Al Alloys
by Saif Haider Kayani, Hafiz Muhammad Salman Ajmal, Byung-Joo Kim, Nho-Kwang Park and Kwangjun Euh
Crystals 2024, 14(6), 559; https://doi.org/10.3390/cryst14060559 - 17 Jun 2024
Viewed by 178
Abstract
This study investigates the impact of varying powder size on porosity, pore parameters, and intermetallic phase reaction during the reactive sintering of porous TiAl alloys. Ti52Al48 alloys were prepared using coarse (200 mesh) and fine (325 mesh) Ti powders through elemental powder metallurgy [...] Read more.
This study investigates the impact of varying powder size on porosity, pore parameters, and intermetallic phase reaction during the reactive sintering of porous TiAl alloys. Ti52Al48 alloys were prepared using coarse (200 mesh) and fine (325 mesh) Ti powders through elemental powder metallurgy and were subsequently sintered at different temperatures, 600 and 1200 °C. Our findings reveal a consistent pore morphology and intermetallic phase microstructure across both alloys. However, samples containing fine Ti powder exhibited a higher number density of small pores compared to those incorporating coarse Ti powders. Additionally, alloys prepared with fine Ti powders demonstrated a higher porosity than those prepared with coarse powders. Consequently, fine Ti powder promoted enhanced diffusion between Ti and Al during sintering, as reflected by the lower onset temperature and enthalpy of intermetallic reaction during sintering. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials)
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23 pages, 30432 KiB  
Article
Application of Organo-Modified Silica Nanoparticles to Improve the Load-Bearing Capacity of Bonded Joints of Dissimilar Steel Substrates
by Anna Guzanová, Dagmar Draganovská, Miroslav Tomáš, Petr Szelag, Nikita Veligotskyi, Miroslav Džupon and Marek Vojtko
Crystals 2024, 14(6), 558; https://doi.org/10.3390/cryst14060558 - 17 Jun 2024
Viewed by 261
Abstract
The paper deals with the joining of dissimilar steels by adhesive bonding. The base materials for the experimental work were deep-drawn low-carbon steel DC04, and hot-dip galvanized HSLA steel HX340LAD+Z. Adhesive bonding was performed using rubber-based and epoxy-based adhesives. The research aimed to [...] Read more.
The paper deals with the joining of dissimilar steels by adhesive bonding. The base materials for the experimental work were deep-drawn low-carbon steel DC04, and hot-dip galvanized HSLA steel HX340LAD+Z. Adhesive bonding was performed using rubber-based and epoxy-based adhesives. The research aimed to verify the importance of surface preparation of steel substrates using a formulation with organically modified silica nanoparticles and epoxy organic functional groups, where one end of the functional group can be incorporated into the organic binder of the coating material and the other end can be firmly bonded to substances of an inorganic nature (metals). Since the binder base of adhesives is very similar to that of coatings, verifying the performance of this surface preparation when interacting with the adhesive is necessary. The load-bearing tensile shear capacity of single-lapped joints and the resistance of the joints against corrosion-induced disbanding in a climate chamber were tested. The energy dissipated by the joints up to fracture was calculated from the load-displacement curves. Bonded joints with organosilane were compared with joints without surface preparation and joints prepared by chroman-free zirconate passivation treatment. Exposure of the joints in the climatic chamber did not cause a relevant reduction in the characteristics of the joints. Organosilicate formulation was proved effective when bonding ungalvanized steels with a rubber-based structural adhesive, where it improves the bond quality between the adhesive and the substrate. Full article
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11 pages, 2495 KiB  
Article
High Mechanical Property and Texture Degree of Hot−Extruded Bi0.905Sb0.095
by Linghao Zhao, Hongcheng Zhang, Degang Zhao, Dawei Wang, Ruiheng Liu and Jianghe Feng
Crystals 2024, 14(6), 557; https://doi.org/10.3390/cryst14060557 - 16 Jun 2024
Viewed by 329
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 [...] Read more.
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. Full article
(This article belongs to the Section Crystalline Metals and Alloys)
28 pages, 10284 KiB  
Article
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 - 16 Jun 2024
Viewed by 160
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 [...] Read more.
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. Full article
(This article belongs to the Section Crystalline Metals and Alloys)
11 pages, 3270 KiB  
Article
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 - 15 Jun 2024
Viewed by 201
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 [...] Read more.
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 (μ312) 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. Full article
(This article belongs to the Section Hybrid and Composite Crystalline Materials)
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21 pages, 5316 KiB  
Article
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
Viewed by 459
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 [...] Read more.
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. Full article
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13 pages, 5877 KiB  
Article
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
Viewed by 288
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 RON,sp of [...] Read more.
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 RON,sp 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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21 pages, 11142 KiB  
Review
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
Viewed by 275
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 [...] Read more.
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. Full article
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13 pages, 2173 KiB  
Article
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
Viewed by 292
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Advanced Materials for Applications in Water Splitting)
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19 pages, 12474 KiB  
Article
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
Viewed by 205
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 [...] Read more.
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 (εr = 430,712; εr = 11,577; tan δ = 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). Full article
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9 pages, 9146 KiB  
Article
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
Viewed by 187
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 [...] Read more.
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. Full article
(This article belongs to the Section Materials for Energy Applications)
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13 pages, 999 KiB  
Article
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
Viewed by 352
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Coordination Complexes: Synthesis, Characterization and Application)
12 pages, 2070 KiB  
Article
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
Viewed by 224
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 [...] Read more.
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. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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14 pages, 4037 KiB  
Article
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
Viewed by 250
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 [...] Read more.
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. Full article
(This article belongs to the Section Materials for Energy Applications)
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12 pages, 3818 KiB  
Article
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
Viewed by 226
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Materials for Applications in Water Splitting and Battery)
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4 pages, 220 KiB  
Editorial
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
Viewed by 309
Abstract
Self-assembly is a key process to obtain auto-organized species from disordered components [...] Full article
(This article belongs to the Special Issue Self-Assembled Complexes: “Love at First Sight”)
5 pages, 164 KiB  
Editorial
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
Viewed by 311
Abstract
In recent years, photonic crystals (PhCs) have garnered significant attention due to their extraordinary ability to control and manipulate light at the nanoscale [...] Full article
(This article belongs to the Special Issue Recent Advances in Photonic Crystal and Optical Devices)
1 pages, 162 KiB  
Correction
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
Viewed by 152
Abstract
There was an error in the original publication [...] Full article
(This article belongs to the Special Issue Hydrogen Embrittlement of Metals)
9 pages, 3236 KiB  
Article
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
Viewed by 303
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 [...] Read more.
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. Full article
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11 pages, 3523 KiB  
Article
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
Viewed by 468
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 [...] Read more.
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. Full article
(This article belongs to the Section Polycrystalline Ceramics)
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10 pages, 1831 KiB  
Article
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
Viewed by 462
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 [...] Read more.
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. Full article
(This article belongs to the Topic Optoelectronic Materials, 2nd Volume)
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17 pages, 2690 KiB  
Article
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
Viewed by 208
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 [...] Read more.
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. Full article
(This article belongs to the Section Crystalline Metals and Alloys)
11 pages, 3305 KiB  
Article
Ferroelectric Domain Intrinsic Radiation Resistance of Lithium Niobate Ferroelectric Single−Crystal Film
by Jiahe Li, Jinlong He, Liya Niu, Hao Lu, Xiaojun Qiao, Bo Zhong, Mingzhu Xun, Xiujian Chou and Wenping Geng
Crystals 2024, 14(6), 537; https://doi.org/10.3390/cryst14060537 - 7 Jun 2024
Viewed by 276
Abstract
The study of the properties of ferroelectric materials against irradiation has a long history. However, anti−irradiation research on the ferroelectric domain has not been carried out. In this paper, the irradiation of switched domain structure is innovatively proposed. The switched domain of 700 [...] Read more.
The study of the properties of ferroelectric materials against irradiation has a long history. However, anti−irradiation research on the ferroelectric domain has not been carried out. In this paper, the irradiation of switched domain structure is innovatively proposed. The switched domain of 700 nm lithium niobate (LiNbO3, LN) thin film remains stable after gamma irradiation from 1 krad to 10 Mrad, which was prepared by piezoresponse force microscopy (PFM). In addition, the changing law of domain wall resistivity is explored through different sample voltages, and it is verified that the irradiated domain wall conductivity is still larger than the domain. This domain wall current (DWC) property can be applied to storage, logic, sensing, and other devices. Based on these, a ferroelectric domain irradiation resistance model is established, which explains the reason at an atomic level. The results open a possibility for exploiting ferroelectric materials as the foundation in the application of space and nuclear fields. Full article
20 pages, 3067 KiB  
Article
Properties of Z1 and Z2 Deep-Level Defects in n-Type Epitaxial and High-Purity Semi-Insulating 4H-SiC
by Paweł Kamiński, Roman Kozłowski, Jarosław Żelazko, Kinga Kościewicz and Tymoteusz Ciuk
Crystals 2024, 14(6), 536; https://doi.org/10.3390/cryst14060536 - 7 Jun 2024
Viewed by 256
Abstract
For the first time, the Z1 and Z2 defects with closely spaced energy levels having negative-U properties are revealed in high-purity semi-insulating (HPSI) 4H-SiC using Laplace-transform photoinduced transient spectroscopy (LPITS). In this material, after switching off the optical [...] Read more.
For the first time, the Z1 and Z2 defects with closely spaced energy levels having negative-U properties are revealed in high-purity semi-insulating (HPSI) 4H-SiC using Laplace-transform photoinduced transient spectroscopy (LPITS). In this material, after switching off the optical trap-filling pulse, either the one-electron or the two-electron thermally stimulated emission from these defects is observed at temperatures 300–400 K. It is found that the former corresponds to the Z10/+ and Z20/+ transitions with the activation energies of 514 and 432 meV, respectively, and the latter is associated with the Z1−/+ and Z2−/+ transitions with the activation energies of 592 meV and 650 meV, respectively. The Z1 and Z2 defect concentrations are found to increase from 2.1 × 1013 to 2.2 × 1014 cm−3 and from 1.2 × 1013 to 2.7 × 1014 cm−3, respectively, after the heat treatment of HPSI 4H-SiC samples at 1400 °C for 3 h in Ar ambience. Using the electrical trap-filling pulse, only the thermal two-electron emission from each defect was observed in the epitaxial 4H-SiC through Laplace-transform deep level transient spectroscopy (LDLTS). The activation energies for this process from the Z1 and Z2 defects are 587 and 645 meV, respectively, and the defect concentrations are found to be 6.03 × 1011 and 2.64 × 1012 cm−3, respectively. It is postulated that the Z1 and Z2 defects are the nearest-neighbor divacancies involving the carbon and silicon vacancies located at mixed, hexagonal (h), and quasi-cubic (k) lattice sites. Full article
(This article belongs to the Special Issue Wide Bandgap Semiconductor: GaN and SiC Material and Device)
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4 pages, 163 KiB  
Editorial
Organic–Inorganic Hybrids: A Class of Material with Infinite Opportunities
by Haoran Lin, Wei Liu and Xin Wu
Crystals 2024, 14(6), 535; https://doi.org/10.3390/cryst14060535 - 6 Jun 2024
Viewed by 283
Abstract
The continuous research interest in organic–inorganic hybrid materials can be attributed to the synergistic or complementary interactions between their organic and inorganic components, which, in turn, opens up a wide array of potential applications [...] Full article
(This article belongs to the Special Issue Organic-Inorganic Hybrids: Synthesis, Property and Application)
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