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14 pages, 4447 KiB

Open AccessArticle

Impurity Oxygen-Triggered α- → β-Si₃N₄ Phase Transformation at 1900 °C

by Hisayuki Imamura, Kazuhiro Kura, Tsunehiro Kawata, Sawao Honda, Toru Asaka and Yuji Iwamoto

Crystals 2023, 13(11), 1572; https://doi.org/10.3390/cryst13111572 - 06 Nov 2023

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Oxide additive-free α- → β-Si₃N₄ phase transformation of a high-purity commercial α-Si₃N₄ powder was investigated at 1600 to 1900 °C under a nitrogen pressure of 980 kPa. The XRD analysis revealed that the α- → β-Si₃ [...] Read more.

Oxide additive-free α- → β-Si₃N₄ phase transformation of a high-purity commercial α-Si₃N₄ powder was investigated at 1600 to 1900 °C under a nitrogen pressure of 980 kPa. The XRD analysis revealed that the α- → β-Si₃N₄ phase transformation proceeded mainly at 1900 °C, and was completed by the extensive 1900 °C heat treatment for 20 h. This phase transformation temperature was 33 °C lower than the theoretical α-Si₃N₄ dissociation temperature and was confirmed as completely different from that often discussed for the liquid-phase sintering of α-Si₃N₄ powder by direct comparison with the phase transformation behavior of a reference powder, α-Si₃N₄ powder doped with 1 mol% Y₂O₃. The unique α- → β-Si₃N₄ phase transformation was further studied by a set of characterization techniques including elemental analysis, HAADF-STEM and STEM-EDS analyses. The results strongly suggested that the oxide additive-free α- → β-Si₃N₄ phase transformation was governed by the formation of a metastable solid solution between α-Si₃N₄ and impurity oxygen of approximately 0.6 wt%, which promoted the dissociation below the theoretical α-Si₃N₄ dissociation temperature to afford thermodynamically favorable β-Si₃N₄. Along with the β-Si₃N₄ formation, the impurity oxygen concentrated at the grain boundaries was released from the sample via the grain boundary diffusion to afford high-purity β-Si₃N₄. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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14 pages, 1613 KiB

Open AccessArticle

Thermodynamic Properties and Equation of State for Tungsten

by Nikolay V. Kozyrev and Vladimir V. Gordeev

Crystals 2023, 13(10), 1470; https://doi.org/10.3390/cryst13101470 - 10 Oct 2023

Cited by 2 | Viewed by 920

Abstract

A high-temperature equation of state for tungsten was constructed in this study using experimental data on its thermodynamic properties, thermal expansion, compressibility, and bulk compression modulus. The totality of experimental data were optimized by the temperature-dependent Tait equation over a pressure range from [...] Read more.

A high-temperature equation of state for tungsten was constructed in this study using experimental data on its thermodynamic properties, thermal expansion, compressibility, and bulk compression modulus. The totality of experimental data were optimized by the temperature-dependent Tait equation over a pressure range from 0 up to 1000 kbar and over a temperature range from 20 K to the melting point. An extended Einstein model was used to describe the temperature dependence of thermodynamic and thermophysical parameters. A linear temperature dependence was embraced for the derivative of the isothermal bulk modulus. The resultant equation of state provides a good fit to the whole set of experimental data within measurement uncertainties associated with individual quantities. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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19 pages, 2224 KiB

Open AccessArticle

Influence of Doping Technology on the Stoichiometry and Features of the Localization of B³⁺ Cations in LiNbO₃:B Single Crystals

by Roman Titov, Alexandra Kadetova, Olga Tokko, Nikolay Sidorov, Mikhail Palatnikov, Natalija Teplyakova, Sofja Masloboeva, Irina Biryukova, Ilja Efremov and Diana Manukovskaya

Crystals 2023, 13(8), 1245; https://doi.org/10.3390/cryst13081245 - 12 Aug 2023

Viewed by 684

Abstract

We have established that relatively simple calculations of the Coulomb interaction in the lattice of doped lithium niobate (LN, LiNbO₃) can confirm the physical properties of real crystals. We have developed a method for the double adjustment of real XRD data [...] Read more.

We have established that relatively simple calculations of the Coulomb interaction in the lattice of doped lithium niobate (LN, LiNbO₃) can confirm the physical properties of real crystals. We have developed a method for the double adjustment of real XRD data for calculations of Coulomb interaction in a LN cluster. The study considers two crystals doped with boron (LN:B); LN:B(1) has been grown from a charge with 0.02 mol% B₂O₃, boron has been introduced by homogeneous doping, LN:B(2) has been grown from a charge with 0.547 mol% B₂O₃, and boron has been introduced by direct solid-state doping. XRD and Rietveld method data have been obtained for these crystals. The obtained data have been used to build a model of the LN cluster; the cluster in the calculations consists of six oxygen octahedra of the LN structure. The cluster configuration has been chosen in such a way that the structure contains two tetrahedral voids. We have studied 10 variants of filling a cluster with intrinsic cations (Li, Nb), defects, and vacancies. There are 10 of them because, in addition to the basic cations in their positions, defects are present in the structure. In terms of the defects used (Nb_Li, Nb_V), we have used only those that Rietveld found for these exact LN:B crystals, and the vacancy in the niobium octahedron (V_Nb) compensates for these defects, according to the models known for LN. The energy of the Coulomb interaction between the cluster structure of a real crystal and the boron cation localized in it in different positions has been calculated for each of the configurations. Calculations have demonstrated that B is more likely to be embedded near a defect than in a regular structure. This means that boron positively influences the local substructure of doped LN crystals, not only structures the melt during crystal growth. Calculations have shown that the type and location of structural defects affect the position of boron in the structure of a LN crystal. Calculations have also shown that LN:B(1) has a more stable structure, including optical damage resistance. The photoinduced light scattering (PILS) patterns and conoscopic patterns confirm this conclusion for the studied LN:B crystals. The information obtained in this study may be useful for interpreting the defective structure of LN crystals co-doped with boron and metals (Mg, Zn, etc.). This will supplement the knowledge available in the literature regarding models that describe the structure of complexly doped LN crystals. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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10 pages, 2662 KiB

Open AccessCommunication

The Enhanced Phase-Forming Capacity of (1–x)Mg_0.95Co_0.05TiO₃-xCa_0.6La_0.8/3TiO₃ Dielectric Ceramics Modified Using Multiple Sintering Aids

by Chung-Long Pan, Chun-Hsu Shen and Kuei-Chih Lin

Crystals 2023, 13(6), 927; https://doi.org/10.3390/cryst13060927 - 09 Jun 2023

Viewed by 755

Abstract

In this study, the phase-forming capacity of 0.9Mg_0.95Co_0.05TiO₃-0.1Ca_0.6La_0.8/3TiO₃ dielectric ceramics was improved by mixing multiple sintering aids (ZnO-B₂O₃) owing to their lower melting point. The mixed-phase systems of [...] Read more.

In this study, the phase-forming capacity of 0.9Mg_0.95Co_0.05TiO₃-0.1Ca_0.6La_0.8/3TiO₃ dielectric ceramics was improved by mixing multiple sintering aids (ZnO-B₂O₃) owing to their lower melting point. The mixed-phase systems of Ca_0.6La_0.8/3TiO₃-modified Mg_0.95Co_0.05TiO₃ dielectric ceramics were verified using XRD diffraction to ensure that the crystallites of different phases were present. The microstructures of the Ca_0.6La_0.8/3TiO₃-modified Mg_0.95Co_0.05TiO₃ dielectric ceramics were observed via SEM and EDS to investigate the relation between element ratios and grains. It was found that the phase-forming capacity of Ca_0.6La_0.8/3TiO₃-modified Mg_0.95Co_0.05TiO₃ was effectively enhanced, compared with the treatment that did not involve mixing multiple sintering aids (ZnO-B₂O₃). Additionally, the microwave dielectric performances of Ca_0.6La_0.8/3TiO₃-modified Mg_0.95Co_0.05TiO₃ dielectric ceramics with multiple sintering aids (ZnO-B₂O₃) strongly depended on the density and morphology of the specimens. When the compositions of 0.9Mg_0.95Co_0.05TiO₃-0.1Ca_0.6La_0.8/3TiO₃ with 1 wt% multiple sintering aids (ZnO-B₂O₃) showed an ε_r value of 22.6, a Qf value of 49,000 GHz, and a τ_f value of −12.8 ppm/°C, the sintering temperature was reduced from 1350 °C to 1150 °C (about 200 °C). When adding a larger amount of multiple sintering aids (ZnO-B₂O₃), the sintering temperature could be reduced by more than 200 °C. This study may promote the use of Ca_0.6La_0.8/3TiO₃-modified Mg_0.95Co_0.05TiO₃ dielectric ceramics. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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11 pages, 5033 KiB

Open AccessArticle

Laser Textured Superhydrophobic SiC Ceramic Surface and the Performance of Condensation Heat Transfer

by Deyuan Lou, Gengxin Lu, Heng Li, Pengjian Chen, Qing Tao, Qibiao Yang and Dun Liu

Crystals 2023, 13(5), 840; https://doi.org/10.3390/cryst13050840 - 19 May 2023

Viewed by 1246

Abstract

Chemical modification is usually utilized for preparing superhydrophobic SiC surfaces, which has the problems of long processing time, high environmental contamination risk, and high cost. To enhance the condensation heat transfer efficiency of SiC, the superhydrophobic SiC surface was fabricated through laser texturing [...] Read more.

Chemical modification is usually utilized for preparing superhydrophobic SiC surfaces, which has the problems of long processing time, high environmental contamination risk, and high cost. To enhance the condensation heat transfer efficiency of SiC, the superhydrophobic SiC surface was fabricated through laser texturing and heat treatment. In this study, the SiC surface was processed by laser texturing with a nanosecond laser, followed by heat treatment. Surface microstructures and compositions were investigated with SEM and XPS, and the heat transfer coefficient of the superhydrophobic SiC surface was tested. The results indicated that the laser-textured SiC surface had a super hydrophilic contact angle of 0°; after heat treatment, SiC ceramic became superhydrophobic (surface contact angle reaches 164°) because organic contamination on the original SiC surface could be cleaned by using laser texturing, which caused a chemical reaction and the formation of SiO₂ on the surface. Moreover, the distribution of relatively low-energy SiO_X was formed after heat treatment; then, SiC ceramic became superhydrophobic. Due to the formation of nanoscale sheet-like protrusion structures by heat treatment, the SiC superhydrophobic surface exhibited typical dropwise condensation, and the condensation heat transfer coefficient reached 331.8 W/(m²·K), which was 2.3 times higher than that of the original surface. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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11 pages, 1538 KiB

Open AccessEditor’s ChoiceArticle

Structure and Anharmonicity of α- and β-Sb₂O₃ at Low Temperature

by Duncan H. Moseley, Craig A. Bridges, Luke L. Daemen, Qiang Zhang, Michael A. McGuire, Ercan Cakmak and Raphaël P. Hermann

Crystals 2023, 13(5), 752; https://doi.org/10.3390/cryst13050752 - 01 May 2023

Viewed by 2035

Abstract

Antimony oxides are important materials for catalysis and flame-retardant applications. The two most common phases,

α

-Sb₂O₃ (senarmontite) and

β

-Sb₂O₃ (valentinite), have been studied extensively. Specific focus has been placed recently on their lattice dynamics properties [...] Read more.

Antimony oxides are important materials for catalysis and flame-retardant applications. The two most common phases,

α

-Sb₂O₃ (senarmontite) and

β

-Sb₂O₃ (valentinite), have been studied extensively. Specific focus has been placed recently on their lattice dynamics properties and how they relate to the

α

-

β

phase transformation and their potential anharmonicity. However, there has not been any direct investigation of anharmonicity in these systems, and a surprising lack of low-temperature structural information has prevented further study. Here, we report the powder neutron diffraction data of both phases of Sb₂O₃, as well as structural information.

α

-Sb₂O₃ behaved as expected, but

β

-Sb₂O₃ revealed a small region of zero thermal expansion along the c axis. Additionally, while the

β

phase matched well with reported atomic displacement parameters, the

α

phase displayed a marked deviation. This data will enable further investigations into these systems. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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19 pages, 6622 KiB

Open AccessArticle

Photocatalytic Azo Dye Degradation Using Graphite Carbon Nitride Photocatalyst and UV-A Irradiation

by Salma A. Al-Zahrani, Mallikarjunagouda B. Patil, Shridhar N. Mathad, Arun Y. Patil, Ahmed Al Otaibi, Najat Masood, Dorsaf Mansour, Anish Khan, Vikas Gupta, Niraj S. Topare, Amita Somya and Manikandan Ayyar

Crystals 2023, 13(4), 577; https://doi.org/10.3390/cryst13040577 - 28 Mar 2023

Cited by 4 | Viewed by 1689

Abstract

The photocatalytic degradation of Acid Red 26 was examined utilizing a graphitic carbon nitride (g-C₃N₄) catalyst and a UV-A light in this study. We investigated how successfully the photocatalytic approach removed Acid Red 26 from synthetic and actual municipal [...] Read more.

The photocatalytic degradation of Acid Red 26 was examined utilizing a graphitic carbon nitride (g-C₃N₄) catalyst and a UV-A light in this study. We investigated how successfully the photocatalytic approach removed Acid Red 26 from synthetic and actual municipal wastewater. Both aqueous matrices allowed for extremely high clearance rates. Wastewater degraded at a slower rate than the other matrices, this might be ascribed to the wastewater’s complicated chemical composition. Using a liquid chromatography-mass spectrometry (LC-MS), the IPs in both synthetic and actual municipal effluent were determined. The photocatalytic degradation mechanisms of Acid Red 26 are hypothesised to comprise oxidation, dealkylation, and methoxy group cleavage based on the observed intermediate products (IPs). Using proven scavengers, we were also able to investigate the role of reactive species in the degradation process and illustrate the significance of h⁺ and O₂^• in the reaction. Chlorococcum sp. and Dunaliella tertiolecta microalgae were also utilised to assess the development of ecotoxicity. We observed low toxicity throughout the process when clean water was used as the matrix, with no production of hazardous IPs. In the case of actual municipal wastewater, there was an early rise in toxicity, which scientists believe was caused by the matrix’s chemical make-up. To lower the toxicity, a heterogeneous photocatalysis was used, and at the end of the treatment, nearly full detoxification was obtained. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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18 pages, 13940 KiB

Open AccessArticle

Characterization, Kinetic Using Deconvolution Techniques and Thermodynamic Study of Synthetic MgHPO₄·3H₂O

by Saifon Kullyakool, Somphob Thompho, Banjong Boonchom and Pesak Rungrojchaipon

Crystals 2023, 13(4), 567; https://doi.org/10.3390/cryst13040567 - 27 Mar 2023

Viewed by 1064

Abstract

MgHPO₄·3H₂O was synthesized via a simple wet reaction and transformed to its final decomposed product, Mg₂P₂O₇ at 873 K. The thermal properties, vibrational modes of block units, and solid phases of the synthetic compounds [...] Read more.

MgHPO₄·3H₂O was synthesized via a simple wet reaction and transformed to its final decomposed product, Mg₂P₂O₇ at 873 K. The thermal properties, vibrational modes of block units, and solid phases of the synthetic compounds have been investigated by TG/DTG/DTA, FTIR, and XRD techniques. The temperature dependence of thermodynamic properties estimated from the DSC data occurred in two regions (before and after the dehydration reaction) indicating a characteristic of the prepared MgHPO₄·3H₂O sample. The dehydration reactions of 3.5 mol of water molecules in the structure overlapped in the temperature of 363–823 K and showed the phase transition at 921 K as revealed by TG/DTG/DTA. The deconvolution technique using the newly modified co-mathematical functions was used to separate the overlapped dehydration steps in the DTG curve, which obtained the three steps. Only the first and second steps were estimated using kinetic triplet parameters (E_a, A, and model), which indicate the single dehydration mechanism with the A_1.25 model and the multi-step of a parallel mechanism with the A_1.6 model, respectively. The data of kinetics and thermodynamics play key points in theoretical study, application development, and industrial production of magnesium phosphates as a theoretical basis. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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18 pages, 16933 KiB

Open AccessArticle

Antibacterial Properties of Three-Dimensional Flower Cluster ZIF-L Modified by N-Doped Carbon Dots

by Jing He, Yuanyuan Xiong, Huaixuan Mu, Peini Li, Yiqing Deng, Wangcai Zou and Qiang Zhao

Crystals 2023, 13(4), 564; https://doi.org/10.3390/cryst13040564 - 25 Mar 2023

Viewed by 1521

Abstract

To overcome the problems of excessive ion release of inorganic antimicrobial agents and the biological toxicity of organic antimicrobial agents, metal organic framework (MOF) materials are attracting attention in the antimicrobial field due to their tunable structural properties and multifunctional applications. Most current [...] Read more.

To overcome the problems of excessive ion release of inorganic antimicrobial agents and the biological toxicity of organic antimicrobial agents, metal organic framework (MOF) materials are attracting attention in the antimicrobial field due to their tunable structural properties and multifunctional applications. Most current studies are limited to zeolitic imidazolate framework-8 (ZIF-8), which has low antimicrobial efficiency by component release. Two-dimensional (2D) zeolitic imidazolate framework nanoleaf (ZIF-L) possesses better antimicrobial effect than ZIF-8 because of the physical destructionto bacteria by its blade tip. However, the in-situ synthesis method of two-dimensional ZIF-L, and the problem of leaf accumulation, limit the wider application of ZIF-L. In this paper, three-dimensional(3D) flower cluster-like ZIF-L (2–3 μm, +31.23 mv), with better antibacterial effects and a wider application range, was prepared by stirring without adding other reagents. To further improve the antibacterial performance of ZIF-L, nitrogen-doped carbon dots (NCDs) were electrostatically absorbed by ZIF-L to obtain NCDs@ZIF-L composites. The NCDs@ZIF-L composites showed over 95% and 85% antibacterial efficiency against E. coli and S. aureus, respectively, at a concentration of 0.25 mg/mL. In addition, polylactic acid (PLA) films mixed with ZIF-L and NCDs@ZIF-L composites with PLA showed good antimicrobial properties, indicating the applicability of ZIF-L and NCDs@ZIF-L composites for antibacterial materials. With a unique three-dimensional crystal shape and positive surface charge, ZIF-L and NCDs@ZIF-L composites exhibited excellent antibacterial properties, which provided a new perspective for the study of antimicrobial materials. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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8 pages, 3072 KiB

Open AccessCommunication

Citrate-Assisted One-Pot Hydrothermal Preparation of Carbonated Hydroxyapatite Microspheres

by Mei-li Qi, Yanling Wu, Cuicui Sun, Haijun Zhang and Shengkun Yao

Crystals 2023, 13(4), 551; https://doi.org/10.3390/cryst13040551 - 23 Mar 2023

Cited by 3 | Viewed by 1178

Abstract

Carbonated hydroxyapatite (CHA) microspheres have aroused wide concern in biofields because of their excellent biological and surface properties. However, the facile preparation of CHA microspheres from organic compounds, especially the microstructural transformation during synthesis, has been rarely reported. In this work, CHA microspheres [...] Read more.

Carbonated hydroxyapatite (CHA) microspheres have aroused wide concern in biofields because of their excellent biological and surface properties. However, the facile preparation of CHA microspheres from organic compounds, especially the microstructural transformation during synthesis, has been rarely reported. In this work, CHA microspheres with an average diameter of 2.528 μm and a BET surface area of 51.0658 m²/g were synthesized via a one-pot hydrothermal method at 180 °C for 10 h by using calcium chloride, diammonium hydrogen phosphate, urea, and trisodium citrate (TSC) with a molar ratio of TSC to Ca of 1:2. The effects of hydrothermal treatment temperature and molar ratio of TSC to Ca on the morphology of the products were investigated. As a chelating agent, TSC is crucial to the formation of CHA microspheres during the hydrothermal homogeneous precipitation process. A possible mechanism of the microstructural transformation from bundle to dumbbell, dumbbell ball, and finally, microspheres regulated by TSC and urea was proposed. The CHA microspheres can be used as effective drug carriers for biomedical applications. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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16 pages, 573 KiB

Open AccessArticle

Complex Assessment of X-ray Diffraction in Crystals with Face-Centered Silicon Carbide Lattice

by Igor I. Bosikov, Nikita V. Martyushev, Roman V. Klyuev, Vadim S. Tynchenko, Viktor A. Kukartsev, Svetlana V. Eremeeva and Antonina I. Karlina

Crystals 2023, 13(3), 528; https://doi.org/10.3390/cryst13030528 - 19 Mar 2023

Cited by 20 | Viewed by 1699

Abstract

X-ray diffraction analysis is essential in studying stacking faults. Most of the techniques used for this purpose are based on theoretical studies. These studies suggest that the observed diffraction patterns are caused by random stacking faults in crystals. In reality, however, the condition [...] Read more.

X-ray diffraction analysis is essential in studying stacking faults. Most of the techniques used for this purpose are based on theoretical studies. These studies suggest that the observed diffraction patterns are caused by random stacking faults in crystals. In reality, however, the condition of randomness for stacking faults may be violated. The purpose of the study was to develop a technique that can be used to calculate the diffraction effects of the axis of the thin plates of twin, new phases, as well as other variations in defective structures. Materials and methods. This was achieved through modern X-ray diffraction methods using differential equations (transformations and Fourier transforms) and the construction of the Ewald sphere, mathematical analysis, mathematical logic, and mathematical modeling (complex Markov chain). Conclusion. The study made it possible to develop a technique for the calculation of the diffraction effects of the axis of the thin plates of twin, new phases and other variations in defective structures. The technique makes it possible to solve several complex, urgent problems related to the calculation of X-ray diffraction for crystals with face-centered lattices containing different types of stacking faults. At the same time, special attention was paid to the correlations between the relative positions of faults. The calculations showed that the proposed method can help to determine the nature and structure of stacking faults by identifying the partial and vertex dislocations limiting them in twin crystals with a face-centered cubic structure of silicon carbide based on X-ray diffraction analysis. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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25 pages, 4859 KiB

Open AccessArticle

Crystallographic, Structural, and Electrical Properties of W⁶⁺ Substituted with Mo⁶⁺ in Crystalline Phases such as TTB Structure

by Hicham Es-soufi, M. I. Sayyed, Aljawhara H. Almuqrin, Raman Rajesh, Alan Rogerio Ferreira Lima, Hssain Bih and Lahcen Bih

Crystals 2023, 13(3), 483; https://doi.org/10.3390/cryst13030483 - 11 Mar 2023

Cited by 2 | Viewed by 1484

Abstract

Owing to their low dielectric loss and high permittivity values, dielectric ceramics have garnered a lot of interest from the scientific and industrial sectors. These properties allow for their downsizing and use in a variety of electronic circuits. This present work focuses on [...] Read more.

Owing to their low dielectric loss and high permittivity values, dielectric ceramics have garnered a lot of interest from the scientific and industrial sectors. These properties allow for their downsizing and use in a variety of electronic circuits. This present work focuses on the impact of the substitution of W⁶⁺ with Mo⁶⁺ on the structural and dielectric features of the crystalline phases in a similar TTB structure within the Ba_0.54Na_0.46Nb_1.29W_(0.37−x)Mo_xO₅ system, with 0 ≤ x ≤ 0.33 mol%. These crystalline phases were elaborated using the conventional solid-state reaction method and analyzed with XRD, Raman, and dielectric techniques. The Rietveld refinement method showed that all these phases are characterized by tetragonal structure and the P4bm space group. The Raman spectra corresponded well to a TTB-like structure, and all the bands were assigned. The dielectric measurements of the prepared ceramic samples facilitated the determination of their phase transition temperature (T_c) and the dielectric responses. This investigation focused on determining dielectric permittivity (ε′) and its correlation with increases in MoO₃ content in the ceramic structure. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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14 pages, 4279 KiB

Open AccessArticle

Three-Dimensional MoS₂ Nanosheet Structures: CVD Synthesis, Characterization, and Electrical Properties

by Sobin Mathew, Johannes Reiprich, Shilpashree Narasimha, Saadman Abedin, Vladislav Kurtash, Sebastian Thiele, Bernd Hähnlein, Theresa Scheler, Dominik Flock, Heiko O. Jacobs and Jörg Pezoldt

Crystals 2023, 13(3), 448; https://doi.org/10.3390/cryst13030448 - 04 Mar 2023

Cited by 1 | Viewed by 1459

Abstract

The proposed study demonstrates a single-step CVD method for synthesizing three-dimensional vertical MoS₂ nanosheets. The postulated synthesizing approach employs a temperature ramp with a continuous N₂ gas flow during the deposition process. The distinctive signals of MoS₂ were revealed via [...] Read more.

The proposed study demonstrates a single-step CVD method for synthesizing three-dimensional vertical MoS₂ nanosheets. The postulated synthesizing approach employs a temperature ramp with a continuous N₂ gas flow during the deposition process. The distinctive signals of MoS₂ were revealed via Raman spectroscopy study, and the substantial frequency difference in the characteristic signals supported the bulk nature of the synthesized material. Additionally, XRD measurements sustained the material’s crystallinity and its 2H-MoS₂ nature. The FIB cross-sectional analysis provided information on the origin and evolution of the vertical MoS₂ structures and their growth mechanisms. The strain energy produced by the compression between MoS₂ islands is assumed to primarily drive the formation of vertical MoS₂ nanosheets. In addition, vertical MoS₂ structures that emerge from micro fissures (cracks) on individual MoS₂ islands were observed and examined. For the evaluation of electrical properties, field-effect transistor structures were fabricated on the synthesized material employing standard semiconductor technology. The lateral back-gated field-effect transistors fabricated on the synthesized material showed an n-type behavior with field-effect mobility of 1.46 cm² V⁻¹ s⁻¹ and an estimated carrier concentration of 4.5 × 10¹² cm⁻². Furthermore, the effects of a back-gate voltage bias and channel dimensions on the hysteresis effect of FET devices were investigated and quantified. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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12 pages, 2097 KiB

Open AccessArticle

Reactive Spark Plasma Sintering and Thermoelectric Properties of Zintl Semiconducting Ca₁₄Si₁₉ Compound

by Doaa Omar A. Ali, Marco Fabbiani, Loïc Coulomb, Simon Bosc, Benjamin Villeroy, Camille Estournès, Claude Estournès, Michael Marek Koza, Mickaël Beaudhuin and Romain Viennois

Crystals 2023, 13(2), 262; https://doi.org/10.3390/cryst13020262 - 02 Feb 2023

Viewed by 1308

Abstract

We present a new reactive spark plasma sintering (RSPS) technique for synthesizing the rhombohedral Ca

_{14}

Si

_{19}

phase. The RSPS approach reduces the synthesis time from several weeks to a few minutes. The RSPS was found to be sufficient for obtaining a [...] Read more.

We present a new reactive spark plasma sintering (RSPS) technique for synthesizing the rhombohedral Ca

_{14}

Si

_{19}

phase. The RSPS approach reduces the synthesis time from several weeks to a few minutes. The RSPS was found to be sufficient for obtaining a high level of purity of the Ca

_{14}

Si

_{19}

under a pressure of 100 MPa for a dwell period of 5 min at a temperature of 900

^{\circ}

C. From electrical resistivity measurements, we were able to determine the energy band gap of Ca

_{14}

Si

_{19}

to

E_{g} = 0.145 (15)

eV. The Seebeck coefficient shows Ca

_{14}

Si

_{19}

as a p-type semiconductor at room temperature. It becomes n-type with increasing temperature pointing to significant bipolar and conduction band contributions due to the narrow bandgap of the compound. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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14 pages, 5298 KiB

Open AccessArticle

The Indentation Size Effect (ISE) of Ag–Cu Alloys

by Marek Šolc, Peter Blaško, Jozef Petrík, Pavol Palfy and Lenka Girmanová

Crystals 2023, 13(1), 91; https://doi.org/10.3390/cryst13010091 - 04 Jan 2023

Cited by 1 | Viewed by 1250

Abstract

The literature regarding the Indentation Size Effect (ISE) in metal alloys is scarce. The content of this article is the study of the relationship between the applied load and the measured values of the Vickers micro-hardness of silver and copper alloys, measured with [...] Read more.

The literature regarding the Indentation Size Effect (ISE) in metal alloys is scarce. The content of this article is the study of the relationship between the applied load and the measured values of the Vickers micro-hardness of silver and copper alloys, measured with a Hanemann hardness tester. The load values ranged between 0.09807 N (10 g) and 0.9807 N (100 g). The size and character of the ISE were evaluated using Meyer’s power law (index n), Proportional Specimen Resistance (PSR) and the Hays–Kendall method. Coins and utility objects of Central European provenance with a silver content of 50 to 99.99% were used as samples. All samples showed a reverse effect (RISE) with a value of n > 2, which is typical for plastic materials. The relatively high variability of the measured micro-hardness and consequently of the index n is related to other factors, such as the age of the sample (age hardening by the precipitation of copper), the uneven degree of deformation and microstructure. The analyzed Ag–Cu alloys show a gradual increase in the Meyer index n with the increase in the silver content, while the ISE has a reverse character throughout the range. The obtained data make it possible to determine the approximate age of artifacts from the mentioned alloys. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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14 pages, 9907 KiB

Open AccessArticle

Formation of α-Hemihydrate Inside of a Gypsum Crystal during the Dehydration Process

by Christian Pritzel, Mohammadamin Emami, Sandra Afflerbach, Manuela Killian and Reinhard Trettin

Crystals 2022, 12(12), 1780; https://doi.org/10.3390/cryst12121780 - 08 Dec 2022

Cited by 2 | Viewed by 2191

Abstract

Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world. During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water to form dihydrate again. Therefore, the dehydration process of gypsum and the [...] Read more.

Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world. During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water to form dihydrate again. Therefore, the dehydration process of gypsum and the rehydration of hemihydrate were investigated. This dehydration process is technically performed in three different ways. Heating up, i.e., in a rotary kiln, leads to a preferred formation of β-hemihydrate, which crystallizes in comparatively small crystals. Similar results can be achieved by recrystallization from gypsum slurry around 100 °C in an autoclave or under a water steam atmosphere. However, in contrast, the recrystallization process here leads to the formation of a larger, needle-like morphology and sometimes branched α-hemihydrate crystals. The synthesis of β-hemihydrate was investigated in detail with a special thermal stage for optical microscopy on natural single gypsum crystals. It was observed that the crystal loses transparency because of the breaking surface of the crystals due to water evaporation. Furthermore, within a deeper layer of the crystal, new crystals become visible but disappear during dehydration of the upper layers. These are expected to be α-hemihydrate. This theory of the formation of α-hemihydrate inside of a gypsum crystal is experimentally proven in the present work. This work firstly shows that the observed crystallization inside of gypsum during dehydration is the formation of alpha-hemihydrate. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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10 pages, 876 KiB

Open AccessArticle

First-Principle Investigation of Hypothetical NiF₄ Crystal Structures

by Tilen Lindič, Anthony Schulz and Beate Paulus

Crystals 2022, 12(11), 1640; https://doi.org/10.3390/cryst12111640 - 15 Nov 2022

Cited by 1 | Viewed by 1447

Abstract

An important synthetic route for the fluorinated organic compounds is electrochemical fluorination (ECF). This is a process taking place on a nickel anode immersed in anhydrous HF. Even though the mechanism is not fully resolved, it is believed that it involves higher valent [...] Read more.

An important synthetic route for the fluorinated organic compounds is electrochemical fluorination (ECF). This is a process taking place on a nickel anode immersed in anhydrous HF. Even though the mechanism is not fully resolved, it is believed that it involves higher valent nickel fluorides formed on the anode. One such compound could be NiF₄. Its synthesis and existence have been reported in the literature. However, its crystal structure has so far remained unknown. In this paper, we present, for the first time, the theoretical study of the possible crystal structure of NiF₄. We investigated six crystal structures of known metal tetrafluorides as possible candidates for NiF₄ by periodic DFT, with the PBE+U method. Of the investigated structures, the most stable polymorph of NiF₄ was found to be of the same crystal structure as RuF₄. The unit cell parameters were calculated to be a = 4.80 Å, b = 5.14 Å, c = 5.18 Å and

β

= 105.26

^{\circ}

. All but one of the investigated structures feature octahedrally coordinated nickel centers with two non-bridging fluorine atoms. In the structure originating from ZrF₄, all six fluorine atoms around the nickel centers are bridging and two are located in the vacancies around the nickel skeleton, not directly bound to nickel. The overall magnetic arrangement in all the investigated structures is antiferromagnetic. A comparison with other binary nickel fluorides supports the experimental findings that NiF₄ is thermodynamically the least stable. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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9 pages, 3500 KiB

Open AccessArticle

Radiation Response Properties of Tb-Doped MgGa₂O₄ Single Crystals

by Yuma Takebuchi, Satoshi Honjo, Kazumitsu Naoe, Takumi Kato, Daisuke Nakauchi, Noriaki Kawaguchi and Takayuki Yanagida

Crystals 2022, 12(11), 1620; https://doi.org/10.3390/cryst12111620 - 12 Nov 2022

Cited by 6 | Viewed by 1623

Abstract

Tb-doped MgGa₂O₄ single crystals (0.3, 1, 3, and 5%) were synthesized by the floating zone method. The synthesized crystals had a single phase of MgGa₂O₄ confirmed by X-ray diffraction and high transparency in the visible wavelength. Tb [...] Read more.

Tb-doped MgGa₂O₄ single crystals (0.3, 1, 3, and 5%) were synthesized by the floating zone method. The synthesized crystals had a single phase of MgGa₂O₄ confirmed by X-ray diffraction and high transparency in the visible wavelength. Tb³⁺ acted as a luminescence center in both photoluminescence (PL) and thermally stimulated luminescence (TSL) processes. In the TSL dose response functions, the minimum detectable dose of the crystals was 0.01 mGy, which was comparable with some commercial dosimetric materials. In the X-ray imaging test taken based on TSL, the spatial resolution of the 1% Tb-doped crystal was estimated to be 8.90 LP/mm (56.2 μm). Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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14 pages, 7663 KiB

Open AccessArticle

Study of the Structural, Optical and Strength Properties of Glass-like (1−x)ZnO–0.25Al₂O₃–0.25WO₃–xBi₂O₃ Ceramics

by Artem L. Kozlovskiy, Aibek S. Seitbayev, Daryn B. Borgekov and Maxim V. Zdorovets

Crystals 2022, 12(11), 1527; https://doi.org/10.3390/cryst12111527 - 27 Oct 2022

Cited by 1 | Viewed by 1120

Abstract

The main purpose of this work is to study the effect of substitution of zinc oxide for bismuth oxide in the composition of (1−x)ZnO–0.25Al₂O₃–0.25WO₃–xBi₂O₃ ceramics, as well as the accompanying processes of phase transformations [...] Read more.

The main purpose of this work is to study the effect of substitution of zinc oxide for bismuth oxide in the composition of (1−x)ZnO–0.25Al₂O₃–0.25WO₃–xBi₂O₃ ceramics, as well as the accompanying processes of phase transformations and their influence on the optical and strength properties of ceramics. The use of these oxide compounds as materials for creating shielding coatings or ceramics is due to the combination of their structural, optical, and strength properties, which make it possible to compete with traditional protective glasses based on rare earth oxide compounds. Interest in these types of ceramics is due to their potential for use as basic materials for shielding ionizing radiation as well as for use as radiation-resistant coatings. The main research methods were X-ray diffractometry to determine the phase composition of ceramics; scanning electron microscopy and energy dispersive analysis to determine the morphological features and isotropy of the distribution of elements in the structure; and UV-V is spectroscopy to determine the optical properties of ceramics. During the studies, it was found that an increase in the Bi₂O₃ concentration leads to the formation of new phase inclusions in the form of orthorhombic Bi₂WO₆ and Bi₂W₂O₉ phases, the appearance of which leads to an increase in the density of ceramics and a change in the dislocation density. An analysis of the strength properties, in particular, hardness and crack resistance, showed that a change in the phase composition of ceramics with an increase in the Bi₂O₃ concentration leads to a significant strengthening of the ceramics, which is due to the effect of the presence of interfacial boundaries as well as an increase in the dislocation density. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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14 pages, 2724 KiB

Open AccessArticle

Study of the Sorption Properties of Natural Zeolite in Relation to Indium(III) and Gallium(III) Cations on the Model Systems

by Gita Sultanbayeva, Aktolkyn Agatayeva, Raushan Kaiynbayeva, Nazym Kozhabekova, Raisa Chernyakova and Umirzak Jussipbekov

Crystals 2022, 12(9), 1220; https://doi.org/10.3390/cryst12091220 - 29 Aug 2022

Cited by 1 | Viewed by 1098

Abstract

This paper presents the systematic studies of the sorption capacity of natural zeolite with respect to In³⁺ and Ga³⁺ cations in the model systems “natural zeolite–In³⁺–H₂O” and “natural zeolite–In³⁺–Ga³⁺–H₂O”, while varying [...] Read more.

This paper presents the systematic studies of the sorption capacity of natural zeolite with respect to In³⁺ and Ga³⁺ cations in the model systems “natural zeolite–In³⁺–H₂O” and “natural zeolite–In³⁺–Ga³⁺–H₂O”, while varying a number of the main process factors. The patterns of sorption of In³⁺ and Ga³⁺ cations by the natural zeolite of the Shankanai deposit are revealed, depending on the zeolite vs. solution ratio, temperature, and time. It is shown that the sorption of In³⁺ cations by natural zeolite can be controlled by the process duration. The longer the process, the less the sorption by natural zeolite. It has been found that the sorption of In³⁺ cations in the “natural zeolite–In³⁺–Ga³⁺–H₂O” model system depends on the amount of zeolite and temperature, and the sorption of Ga³⁺ cations depends on the temperature and time. The physicochemical characteristics of the spent sorbents confirm the sorption of the cations, present in the systems under study. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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Review

Jump to: Research

15 pages, 1523 KiB

Open AccessReview

Advanced and Biomedical Applications of Schiff-Base Ligands and Their Metal Complexes: A Review

by Alina Soroceanu and Alexandra Bargan

Crystals 2022, 12(10), 1436; https://doi.org/10.3390/cryst12101436 - 12 Oct 2022

Cited by 38 | Viewed by 5212

Abstract

Because of their importance in a variety of interdisciplinary study domains, Schiff-base ligands have performed a significant role in the evolution of contemporary coordination chemistry. This almost-comprehensive review covers all the aspects and properties of complexes, starting from the Schiff-base ligands. Our work [...] Read more.

Because of their importance in a variety of interdisciplinary study domains, Schiff-base ligands have performed a significant role in the evolution of contemporary coordination chemistry. This almost-comprehensive review covers all the aspects and properties of complexes, starting from the Schiff-base ligands. Our work is centered on the eloquent advances that have been developed since 2015, with special consideration to recent developments. Schiff-base ligands and their complexes are adaptable compounds obtained from the condensation of two compounds: a carbonyl with an amino. The correspondent metal complexes have been shown to have antifungal, antibacterial, antioxidant, antiproliferative, and antiviral properties. This review begins with a short introduction to Schiff-base ligands and their metal complexes. It stands out in the recent advancements in the Schiff-base coordination chemistry domain and its future prospects as a potential bioactive core. Additionally, the review contains knowledge about the antioxidant, redox, and catalytic activities of the Schiff-base complexes, with important future applications in the obtaining of new compounds and materials. Full article

(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)

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