Crystals

22 pages, 3566 KB

Open AccessArticle

Numerical Investigation of Thermal Diode-Based Elastocaloric Heat Pump Working with Different Crystalline Refrigerants and Thermoelectric Switches

by Luca Cirillo, Vincenzo Orabona, Lucrezia Verneau, Sabrina Gargiulo, Claudia Masselli and Adriana Greco

Crystals 2026, 16(2), 153; https://doi.org/10.3390/cryst16020153 - 22 Feb 2026

Viewed by 333

Abstract

Elastocaloric cooling is an emerging solid-state refrigeration technology that leverages the latent heat exchange of shape memory alloys under mechanical stress. This study investigates the energy performance of a solid-to-solid elastocaloric cooling heat pump to enhance heat transfer efficiency and overall system performance. [...] Read more.

Elastocaloric cooling is an emerging solid-state refrigeration technology that leverages the latent heat exchange of shape memory alloys under mechanical stress. This study investigates the energy performance of a solid-to-solid elastocaloric cooling heat pump to enhance heat transfer efficiency and overall system performance. A Matlab-based numerical model, developed using the finite volume method, was employed to simulate the system. The energy performances of the elastocaloric heat pump are analyzed by varying the frequency of the cycle, the elastocaloric refrigerants, and the types of thermal diodes, from ideal up to realistic Peltier switches. The results demonstrate that the strategic use of thermal diodes significantly improves heat flow directionality, reducing thermal losses and enhancing the efficiency of the elastocaloric cooling process with a system that employs a realistic Peltier thermal diode, guaranteeing specific cooling powers up to 6500 W kg⁻¹. The maximum COPs of the system with ideal thermal diodes range from 60 to 10. These findings contribute to the development of more efficient solid-state cooling technologies, offering a viable alternative to conventional systems, especially for electronic circuit cooling applications. Full article

(This article belongs to the Special Issue Applications of Crystalline Materials in Elastocaloric Devices)

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13 pages, 2021 KB

Open AccessArticle

Time-Dependent Evolution of Nanostructure Formation on CdI₂ Crystal Surfaces

by Ivan Rovetskii, Halyna Klym, Ivan Karbovnyk, Marina Konuhova, Nadezda Kongi and Anatoli I. Popov

Crystals 2026, 16(2), 152; https://doi.org/10.3390/cryst16020152 - 22 Feb 2026

Viewed by 335

Abstract

The time evolution of nanoscale structure formation on the surface of CdI₂ crystals grown both from the melt and from the gas phase is investigated. Atomic force microscopy was used to show that, already at the initial stages of exposure to air [...] Read more.

The time evolution of nanoscale structure formation on the surface of CdI₂ crystals grown both from the melt and from the gas phase is investigated. Atomic force microscopy was used to show that, already at the initial stages of exposure to air at room temperature, island-shaped nanostructures form, which subsequently aggregate into nanoclusters as the exposure time increases. Similar nanostructures, including nanopores and nanoclusters, are observed for CdI₂ crystals grown from the gas phase after prolonged exposure to air. Photoluminescence spectroscopy indicates that the formed nanoclusters are consistent with the presence of cadmium hydroxide (Cd(OH)₂) and cadmium oxide (CdO). The formation of nanostructures determines the time evolution of the low-temperature luminescence spectra of CdI₂ crystals. Additional bands with maxima at 1.87 eV and long-wavelength luminescence in the region with a maximum at 1.68 eV appear in the spectral structure. These results highlight the close relationship between surface structural evolution and the time-dependent optical properties of CdI₂. Full article

(This article belongs to the Special Issue Properties and Synthesis of Luminescent Materials)

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20 pages, 18226 KB

Open AccessArticle

Study on Stress Corrosion Resistance of Multiphase Composite Nanobainitic Steel via Isothermal Treatment

by Qian Yang, Jing Zhao, Junjie Wang, Yanru Zhang, Yanhui Wang, Qiang Li, Wanshuo Sun, Yanling Sun, Wei Xiong, Huafeng Ding, Zhanbing Wang and Mingkun Xu

Crystals 2026, 16(2), 151; https://doi.org/10.3390/cryst16020151 - 21 Feb 2026

Viewed by 274

Abstract

This study examines the electrochemical behavior and slow strain rate tensile (SSRT) properties of 67Si2CrNiAlMnMoCu steel featuring a multiphase nanobainitic microstructure consisting of bainitic ferrite (BF), retained austenite (RA), and martensite (M). Electrochemical measurements reveal that both the corrosion tendency and dissolution rate [...] Read more.

This study examines the electrochemical behavior and slow strain rate tensile (SSRT) properties of 67Si2CrNiAlMnMoCu steel featuring a multiphase nanobainitic microstructure consisting of bainitic ferrite (BF), retained austenite (RA), and martensite (M). Electrochemical measurements reveal that both the corrosion tendency and dissolution rate decrease with extended austempering time, with the sample austempered at 220 °C for 21 h showing the lowest corrosion susceptibility. SSRT results indicate that specimens with a nearly fully bainitic microstructure exhibit increased strength sensitivity to stress corrosion. Notably, the specimen austempered at 240 °C for 9 h demonstrates excellent corrosion resistance while retaining favorable overall mechanical properties, exhibiting a tensile strength-based stress corrosion cracking sensitivity coefficient as low as 4.1%. Full article

(This article belongs to the Special Issue Crystallization of High-Performance Metallic Materials (3rd Edition))

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10 pages, 1173 KB

Open AccessArticle

Effect of Grain-Size Control on Mechanical and Optical Properties of ZrSi₂ Membranes for Extreme Ultraviolet Pellicles

by Won Jin Kim, Seong Ju Wi, Seungchan Moon, Junho Hong, Taeho Lee, Young Wook Park and Jinho Ahn

Crystals 2026, 16(2), 150; https://doi.org/10.3390/cryst16020150 - 20 Feb 2026

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Abstract

Extreme ultraviolet (EUV) pellicles must exhibit high optical transmittance, thermal, and mechanical stability to withstand the demands of semiconductor fabrication. ZrSi₂ has attracted attention as a pellicle material due to its excellent optical characteristics. The thickness of ZrSi₂ films is being [...] Read more.

Extreme ultraviolet (EUV) pellicles must exhibit high optical transmittance, thermal, and mechanical stability to withstand the demands of semiconductor fabrication. ZrSi₂ has attracted attention as a pellicle material due to its excellent optical characteristics. The thickness of ZrSi₂ films is being reduced to enhance EUV transmittance (EUVT). Since the mechanical strength of nanoscale thin films can be influenced by grain-size effects described by either the Hall–Petch or inverse Hall–Petch relationship, grain-size control becomes critical. In this study, ZrSi₂/SiN_x free-standing membranes with different ZrSi₂ grain sizes were fabricated by sputter deposition followed by annealing at 425–600 °C. Grazing incidence X-ray diffraction analysis confirmed that the ZrSi₂ thin films retained their orthorhombic structure up to 600 °C. Scanning transmission electron microscopy showed a gradual increase in grain size with increasing annealing temperature. EUVT remained almost unchanged regardless of the ZrSi₂ grain size. In contrast, the ultimate tensile strength increased with grain size up to 64 nm and decreased with further grain growth. These results indicate that although the optical properties of ZrSi₂-based EUV pellicles are grain-size independent, their mechanical strength can be optimized through microstructural engineering, consistent with the Hall–Petch relationship. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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25 pages, 8027 KB

Open AccessReview

Magnetic Barkhausen Noise in Steels: Fundamentals, Crystallographic Texture, Stress–Microstructure Coupling, and Industrial Applications

by Polyxeni Vourna, Pinelopi P. Falara, Aphrodite Ktena, Evangelos V. Hristoforou and Nikolaos D. Papadopoulos

Crystals 2026, 16(2), 149; https://doi.org/10.3390/cryst16020149 - 19 Feb 2026

Cited by 1 | Viewed by 424

Abstract

Magnetic Barkhausen noise (MBN) analysis has recently emerged as a powerful nondestructive tool for probing crystallographic orientation, phase transformation, and microstructural stress distribution in ferromagnetic materials. This review aims to summarize recent advances in understanding the relationship between crystallographic texture, dislocation density, and [...] Read more.

Magnetic Barkhausen noise (MBN) analysis has recently emerged as a powerful nondestructive tool for probing crystallographic orientation, phase transformation, and microstructural stress distribution in ferromagnetic materials. This review aims to summarize recent advances in understanding the relationship between crystallographic texture, dislocation density, and magnetic domain dynamics across different classes of steels and surface coatings. Emphasis is placed on the influence of crystal structure symmetry, residual stress gradients, and coating–substrate interactions on the MBN response. The article also discusses recent modeling approaches and potential integration of MBN with complementary techniques such as EBSD and XRD for microstructural diagnostics and materials design. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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24 pages, 6102 KB

Open AccessArticle

Nucleation Studies of Lactobacillus brevis Alcohol Dehydrogenases in a Stirred Crystallizer Monitored by In Situ Multi-Angle Dynamic Light Scattering (MADLS)

by Julian Mentges, Daniel Bischoff and Dirk Weuster-Botz

Crystals 2026, 16(2), 148; https://doi.org/10.3390/cryst16020148 - 19 Feb 2026

Viewed by 352

Abstract

Nucleation remains one of the least understood steps during protein crystallization, although it strongly impacts product quality attributes, including total crystal numbers, final crystal size distributions, and thus downstream processing. In this work, the nucleation behavior of Lactobacillus brevis alcohol dehydrogenase (Lb [...] Read more.

Nucleation remains one of the least understood steps during protein crystallization, although it strongly impacts product quality attributes, including total crystal numbers, final crystal size distributions, and thus downstream processing. In this work, the nucleation behavior of Lactobacillus brevis alcohol dehydrogenase (LbADH) wild type (WT) and five mutants (Q207D, Q126H, K32A, D54F, and T102E) is investigated in a stirred 7 mL crystallizer monitored by in situ multi-angle dynamic light scattering (MADLS). Nucleation was studied with highly pure homotetrameric LbADHs by establishing a crystallization, lyophilization, and re-solubilization protocol combined with size exclusion chromatography (SEC) and size exclusion high-performance liquid chromatography (SE-HPLC), yielding tetramer purities above 94% and removing low molecular weight impurities. During stirred batch crystallizations initiated by the addition of polyethyleneglycol 550 monomethyl ether (PEG 550 MME), SEC and SE-HPLC revealed decreasing tetramer peak areas but essentially constant peak apex positions, indicating that no long-lasting oligomeric intermediates accumulate at detectable levels. Time-resolved MADLS measurements using a custom-made flow-through cuvette in a bypass to the stirred crystallizer uncovered transient cluster populations. All protein variants exhibited an initial tetramer peak, followed by the formation of larger aggregates and a rapid rise in signal above a hydrodynamic diameter of 1000 nm, coinciding with the onset of macroscopic turbidity. A simple mesoscale nucleation model was formulated, yielding end-of-nucleation times, crystallized fractions, critical soluble concentrations, and apparent nucleation rate constants. The crystal contact mutations modulate both the timing and magnitude of the nucleation burst (rapid build-up of nuclei/cluster populations). The mutant Q207D showed strongly attenuated nucleation compared to the WT, whereas the other mutants (K32A, D54F, and particularly T102E) display markedly accelerated nucleation at nearly invariant critical concentrations. The combined workflow demonstrates how in situ MADLS, together with a tailored kinetic description, can provide mechanistic insight into protein nucleation in stirred batch crystallizers. Full article

(This article belongs to the Section Biomolecular Crystals)

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12 pages, 2331 KB

Open AccessArticle

Structural and Proton Conduction Modifications in RbH₂PO₄ Crystals upon Heating Under Different Environments

by Cristian E. Botez and Alex D. Price

Crystals 2026, 16(2), 147; https://doi.org/10.3390/cryst16020147 - 17 Feb 2026

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Abstract

We used synchrotron X-ray diffraction (XRD) and ac-impedance spectroscopy (AIS) to uncover the structural and chemical modifications undergone by RbH₂PO₄ (RDP) at intermediate temperatures (150 °C < T < 300 °C) and investigate their relationship with RDP’s proton conductivity, σ. [...] Read more.

We used synchrotron X-ray diffraction (XRD) and ac-impedance spectroscopy (AIS) to uncover the structural and chemical modifications undergone by RbH₂PO₄ (RDP) at intermediate temperatures (150 °C < T < 300 °C) and investigate their relationship with RDP’s proton conductivity, σ. Nyquist plots collected on RDP samples sealed in a small volume (~50 mL) of dry air show a gradual increase in σ upon heating from 180 to 260 °C, but not the three-order-of-magnitude superprotonic jump observed in the Cs-based compound CsH₂PO₄ (CDP) within the same temperature range. Correspondingly, XRD measurements using synchrotron radiation (λ = 0.922 Å) on RDP crystalline powders sealed in a quartz capillary exhibit no evidence of a monoclinic-to-cubic superprotonic phase transition like the one observed in CDP. Instead, these temperature-resolved powder XRD patterns demonstrate that the intermediate-temperature RDP monoclinic phase (P2₁/m, a = 7.733 Å, b = 6.189 Å, c = 4.793 Å, and β = 109.21 deg) persists up to the melting point of the title compound. Our most significant finding comes from heating RDP under high pressure (P = 1 GPa), which leads to markedly different structural behavior. Indeed, our full profile refinements against XRD data collected on RDP crystals compressed at ~1 GPa show evidence of a polymorphic phase transition (at T_c = 300 °C) to a high-temperature cubic phase (Pm-3m, a = 4.784 Å) that is isomorphic with its CDP counterpart. This is significant, as it indicates that the superprotonic conduction in phosphate solid acids is not cation-specific, and a general highly efficient proton conduction mechanism is present in the high-temperature phases of these materials. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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21 pages, 3618 KB

Open AccessArticle

Chemical Controls on the Green Coloration of the Novel Gem Quartzite “Feizhoucui”: A CIE L*a*b* Colorimetric Study

by Jie Hu, Pengyu Li, Yushu Yang, Ling Yang, Nai Wang and Ying Guo

Crystals 2026, 16(2), 145; https://doi.org/10.3390/cryst16020145 - 17 Feb 2026

Viewed by 504

Abstract

This study investigates the mineralogical composition, color origin, and chromatic classification of “Feizhoucui”, a distinctive green quartzite. Analyses of 54 samples via EPMA, UV-Vis spectroscopy, and colorimetry revealed that its characteristic color is primarily attributed to barian–chromian muscovite, occurring as vein-like or spotted [...] Read more.

This study investigates the mineralogical composition, color origin, and chromatic classification of “Feizhoucui”, a distinctive green quartzite. Analyses of 54 samples via EPMA, UV-Vis spectroscopy, and colorimetry revealed that its characteristic color is primarily attributed to barian–chromian muscovite, occurring as vein-like or spotted associated minerals within a quartz matrix. The chromophoric muscovite’s crystal chemical formula was calculated as (K₀.₇₁Na₀.₀₅Ba₀.₂₀)₀.₉₆ (Al₁.₆₆Mg₀.₁₆Cr₀.₂₂Fe₀.₀₃Ti₀.₀₂)₂.₀₉ (Si₃.₀₄Al₀.₉₆)₄O₁₀(OH)₂. UV-Vis spectra confirm that the green hue arises from Cr³⁺ absorption bands at 610–625 nm and 430–460 nm, while Fe content exerts a minor influence by inducing a red shift of the ~518 nm absorption minimum, thereby reducing the hue angle h°. Cr concentration is the dominant factor, correlating positively with chroma C* and negatively with lightness L*. Quartzite crystallinity negatively correlates with chroma C*, indicating that higher defectivity promotes the incorporation of more color-contributing muscovite. Based on K-means clustering of color data, “Feizhoucui” is classified into three commercial grades: Fancy Intense, Fancy Deep, and Fancy. Full article

(This article belongs to the Special Issue In Situ Study of Mineralogy, Gemology, and Geochemistry and Advances in Gem Resource Exploration)

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13 pages, 7141 KB

Open AccessArticle

The Influence of Coating Thickness and Interface Microcracks on Contact Stresses in Ceramic Bearings: A Discrete Element Study

by Ying Li, Xiaojiao Gu, Jinghua Li, Xiaozheng Xu and He Lu

Crystals 2026, 16(2), 146; https://doi.org/10.3390/cryst16020146 - 16 Feb 2026

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Abstract

This paper investigates the contact stress induced by a rigid sphere sliding on a coating-ceramic system. A discrete element model incorporating a ceramic substrate, a surface coating, and a rigid sphere is developed. The influences of the coating grain elastic modulus, coating surface [...] Read more.

This paper investigates the contact stress induced by a rigid sphere sliding on a coating-ceramic system. A discrete element model incorporating a ceramic substrate, a surface coating, and a rigid sphere is developed. The influences of the coating grain elastic modulus, coating surface friction coefficient, coating thickness, and interface microcrack defects on the stress distribution within the system are analyzed. The results indicate that a higher coating-to-substrate elastic modulus ratio increases the overall stress but reduces the interfacial shear stress. A lower surface friction coefficient is more beneficial for hard coatings. The relatively optimal coating thickness (h/a) is approximately 0.5. When interface microcrack defects are present, stress concentrations occur at their locations. Longer interface microcracks lead to greater stress concentration, and the interfacial concentrated stress increases with crack length. Full article

(This article belongs to the Section Polycrystalline Ceramics)

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9 pages, 1321 KB

Open AccessArticle

Softening of Hard Magnetic Behavior and the Maximum Coercive Field in Zr₂RhTl as Revealed by Effective Field Theory

by Semih Doğruer, Ziya Merdan and Yasin Göktürk Yıldız

Crystals 2026, 16(2), 144; https://doi.org/10.3390/cryst16020144 - 16 Feb 2026

Cited by 1 | Viewed by 496

Abstract

The present study investigated the magnetic hysteresis properties (coercivity and remanent magnetization) of the Zr₂RhTl Heusler alloy using effective field theory (EFT). The study found that the coercive field of Zr₂RhTl reaches a maximum at a specific critical temperature, [...] Read more.

The present study investigated the magnetic hysteresis properties (coercivity and remanent magnetization) of the Zr₂RhTl Heusler alloy using effective field theory (EFT). The study found that the coercive field of Zr₂RhTl reaches a maximum at a specific critical temperature, T_ch, at which the hardness of magnetic materials increases with the coercive field. This behavior is called the “critical hardness temperature (T_ch)”. The hardness of the Zr₂RhTl Heusler alloy increases with temperature until T_ch, reaching a maximum at T_ch. In contrast, it exhibits soft magnetic behavior at T < T_ch and T > T_ch. We suggest that this maximum hardness behavior can enable a new class of thermo-hardness sensors (THSs) and actuators (THAs). Full article

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

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27 pages, 10016 KB

Open AccessArticle

The Effect of Sintering Atmosphere and Temperature on Densification, Grain Growth Behavior and Electrical Properties of 0.685(Na_0.5Bi_0.5)TiO₃-0.065BaTiO₃-0.25SrTiO₃ Ceramics

by Nazım Ecebaş, Thi Huyen Tran Tran, John G. Fisher, Jong-Sook Lee, Woo-Jin Choi, Yeon-Bee Han and Wook Jo

Crystals 2026, 16(2), 143; https://doi.org/10.3390/cryst16020143 - 16 Feb 2026

Viewed by 861

Abstract

(Na_0.5Bi_0.5)TiO₃-BaTiO₃-SrTiO₃-based lead-free piezoelectric ceramics are one of the possible replacements for Pb(Zr_1−xTi_x)O₃. Although they are considered a promising alternative actuator material due to their large electric-field-induced strains, [...] Read more.

(Na_0.5Bi_0.5)TiO₃-BaTiO₃-SrTiO₃-based lead-free piezoelectric ceramics are one of the possible replacements for Pb(Zr_1−xTi_x)O₃. Although they are considered a promising alternative actuator material due to their large electric-field-induced strains, they have several drawbacks, such as large strain hysteresis and the requirement of a high electric field to obtain large electric-field-induced strains. Sintering parameters strongly influence the electrical properties. Thus, the effect of sintering parameters, including atmosphere (air/oxygen), temperature (1150 °C~1250 °C) and holding time (1~20 h) on the sintering behavior of 0.685(Na_0.5Bi_0.5)TiO₃-0.065BaTiO₃-0.25SrTiO₃ electroceramics was studied. Then, the influence of sintering atmosphere on the piezoelectric, ferroelectric and dielectric properties of 0.685(Na_0.5Bi_0.5)TiO₃-0.065BaTiO₃-0.25SrTiO₃ electroceramics sintered at 1250 °C for 1 h was investigated. Sintering in oxygen improves density and restrains grain growth including abnormal grain growth. 0.685(Na_0.5Bi_0.5)TiO₃-0.065BaTiO₃-0.25SrTiO₃ electroceramics sintered in oxygen exhibit smaller grain size, higher density, similar inverse piezoelectric coefficient d₃₃* and lower strain hysteresis compared to air-sintered samples. The effect of sintering atmosphere on grain growth is explained using the mixed control mechanism of boundary migration. Full article

(This article belongs to the Special Issue Recent Research on Piezoelectric Ceramics)

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16 pages, 27509 KB

Open AccessArticle

Enhancing 4H-SiC Lapping Performance: Diamond and Boron Carbide Composite Abrasives Effects on Material Removal and Subsurface Damage

by Xiaoming Sui, David Wei Zhang and Lin Zhang

Crystals 2026, 16(2), 142; https://doi.org/10.3390/cryst16020142 - 16 Feb 2026

Viewed by 410

Abstract

Silicon carbide (SiC) substrates have been widely adopted in high-performance applications such as power electronics, optoelectronics, and semiconductors. However, achieving high-quality processing remains a formidable challenge due to SiC’s inherent hardness and brittleness. This study investigates the effects of diamond and boron carbide [...] Read more.

Silicon carbide (SiC) substrates have been widely adopted in high-performance applications such as power electronics, optoelectronics, and semiconductors. However, achieving high-quality processing remains a formidable challenge due to SiC’s inherent hardness and brittleness. This study investigates the effects of diamond and boron carbide (B₄C) abrasives on material removal rate (MRR) and surface roughness during the lapping of SiC substrates. The results demonstrate that the mix ratio of diamond to B₄C significantly affects the roughness of the lapped substrates. Increasing B₄C proportions results in lower Sa values. Nonetheless, excessive B₄C powder leads to insufficient abrasive lapping force. Furthermore, finer B₄C powder contributes to higher surface roughness and higher SiC removal rate. Additionally, the influence of different diamond powder sizes on the depth of subsurface damage (SSD) of lapped SiC substrates was evaluated using an atmospheric inductively coupled plasma (ICP) etching method. As the diamond particle size increased from 3 μm to 4 μm, the SSD depth rose from 1.56 μm to 2.16 μm. Furthermore, this study elucidates the lapping removal process of silicon carbide substrate from the mechanism, which can provide actionable guidance for refining lapping techniques in 4H-SiC substrate manufacturing. Full article

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22 pages, 6139 KB

Open AccessArticle

Structural, Dielectric, and Electrochemical Properties of Lithium Triflate Doped Ghatti Gum/Xanthan Gum/PVA Solid Polymer Electrolytes for Supercapacitors

by Sekar Snekha, Duraikkan Vanitha, Karuppasamy Sundaramahalingam, Abdul Samad Shameem, Nallaperumal Nallamuthu, Arumugam Murugan and Muthaiah Shellaiah

Crystals 2026, 16(2), 141; https://doi.org/10.3390/cryst16020141 - 15 Feb 2026

Viewed by 403

Abstract

A novel Lithium triflate-incorporated Solid Polymer Electrolyte (SPE) has been developed by using the optimized blend of Ghatti Gum (GG) and Xanthan Gum (XG) with a biodegradable synthetic polymer, Polyvinyl alcohol (PVA), ethylene glycol as a plasticizer, and formaldehyde as a cross-linker for [...] Read more.

A novel Lithium triflate-incorporated Solid Polymer Electrolyte (SPE) has been developed by using the optimized blend of Ghatti Gum (GG) and Xanthan Gum (XG) with a biodegradable synthetic polymer, Polyvinyl alcohol (PVA), ethylene glycol as a plasticizer, and formaldehyde as a cross-linker for energy storage applications. They are examined by X-ray diffraction, Fourier transform infrared spectroscopy, and electrochemical impedance analysis. The frequency-dependent conductivity adheres to Joshner’s universal power law, with the TF10 composition achieving the higher ionic conductivity of 2.73 × 10⁻⁵ S cm⁻¹. Temperature-dependent conductivity confirms Arrhenius-type behavior and shows a low activation energy of 0.15 eV that supports facile ion transport. The conduction process in TF10 follows the Correlated Barrier Hopping (CBH) model. Dielectric and modulus investigations indicate relaxation dynamics with the shorter relaxation time (6.45 × 10⁻⁶ s) from tangent loss spectra. From the SEM analysis, the uniform distribution and the porous nature of the electrode activated carbon are confirmed. A supercapacitor is assembled with TF10 displays electric double-layer capacitive features, delivering a specific capacitance of 7.1 Fg⁻¹ at 15 mVs⁻¹. Charge–discharge analysis reveals energy and power densities of 2.52 Wh kg⁻¹ and 2500 W kg⁻¹, respectively, for the supercapacitor. Full article

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

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15 pages, 6478 KB

Open AccessArticle

Growth and Characterization of Multicomponent, Equimolar Cubic Solid-Solution Crystals in the CaF₂–SrF₂–BaF₂–NdF₃ System

by Irina I. Buchinskaya, Nikolay I. Sorokin, Pavel A. Popov and Denis N. Karimov

Crystals 2026, 16(2), 140; https://doi.org/10.3390/cryst16020140 - 15 Feb 2026

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Abstract

Equimolar crystals of a high-entropy Ca_0.25Sr_0.25Ba_0.25Nd_0.25F_2.25 (CaSrBaNdF₉) fluoride solid solution were grown from a melt by the Bridgman technique, and their optical, electrical, and thermal properties were studied for the first time. [...] Read more.

Equimolar crystals of a high-entropy Ca_0.25Sr_0.25Ba_0.25Nd_0.25F_2.25 (CaSrBaNdF₉) fluoride solid solution were grown from a melt by the Bridgman technique, and their optical, electrical, and thermal properties were studied for the first time. This solid solution crystallizes in a fluorite-type structure (space group Fm-3m with lattice parameter a = 5.807 Å), is transparent over a wide spectral range, and has a refractive index of n_D = 1.5035(5). In terms of ionic conductivity (σ_dc increases monotonically from 3.7 × 10⁻⁵ to 3.9 × 10⁻⁴ S/cm in the studied temperature range of 643–810 K), it significantly exceeds the parameters of binary and ternary NdF₃-based single crystals, such as M_1−xNd_xF_2+x (M = Ca, Sr, Ba; x = 0.24–0.25) and Ca_0.58Sr_0.21Nd_0.21F_2.21. The grown multicomponent material is a hard (H_V~3.6 GPa) isomorphic-capacious crystalline matrix for various applications in solid-state ionics, optics and photonics, and opens up prospects for the development of new functional isotropic optical crystalline materials in quaternary CaF₂–SrF₂–BaF₂–RF₃ and higher-order complex fluoride systems nMF₂–mRF₃, where n + m ≥ 4, M and R are ions of alkaline earth and rare earth elements, respectively. Full article

(This article belongs to the Special Issue Polymorphism and Phase Transitions in Crystal Materials)

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19 pages, 1714 KB

Open AccessArticle

Effects of Uniaxial Distortion on the Stability of Square Skyrmion Crystals in Noncentrosymmetric Magnets

by Satoru Hayami

Crystals 2026, 16(2), 139; https://doi.org/10.3390/cryst16020139 - 14 Feb 2026

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Abstract

We theoretically investigate the influence of uniaxial distortion on the stability of square skyrmion crystals, which are described as double-Q spin textures composed of two orthogonal spiral modulations, in noncentrosymmetric magnets. An effective spin model incorporating momentum-resolved frustrated exchange interactions and Dzyaloshinskii–Moriya [...] Read more.

We theoretically investigate the influence of uniaxial distortion on the stability of square skyrmion crystals, which are described as double-Q spin textures composed of two orthogonal spiral modulations, in noncentrosymmetric magnets. An effective spin model incorporating momentum-resolved frustrated exchange interactions and Dzyaloshinskii–Moriya (DM) interactions is analyzed using simulated-annealing calculations at low temperatures. The results reveal that uniaxial distortion drives a transformation from the double-Q square skyrmion crystal to a single-Q tilted conical spiral or vertical spiral state. The low-temperature phase diagrams further show that the stability region of the skyrmion crystal expands with increasing the magnitude of the DM interaction, making the phase more robust against the uniaxial anisotropy between exchange interactions parallel and perpendicular to the distortion axis. This study provides insight into how uniaxial strain and DM interactions cooperatively influence the formation and stability of skyrmion crystal phases in noncentrosymmetric magnetic systems. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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13 pages, 2121 KB

Open AccessArticle

Study on Dislocation Decomposition Mechanisms and Crack Propagation Modes in a Re/Ru Single-Crystal Nickel-Based Alloy During Room-Temperature Tensile Testing

by Ning Tian, Shunke Zhang, Shulei Sun, Xiaojuan Shang, Xingda Qu, Liyuan Wang, Zhiying Xie and Danping Dang

Crystals 2026, 16(2), 138; https://doi.org/10.3390/cryst16020138 - 13 Feb 2026

Viewed by 303

Abstract

Through room-temperature tensile testing, microstructural observation, and comparative analysis of dislocation configurations, this study investigates the deformation and damage behavior of a high-concentration Re/Ru single-crystal alloy. The results show that the alloy possesses excellent mechanical properties at room temperature, with a tensile strength [...] Read more.

Through room-temperature tensile testing, microstructural observation, and comparative analysis of dislocation configurations, this study investigates the deformation and damage behavior of a high-concentration Re/Ru single-crystal alloy. The results show that the alloy possesses excellent mechanical properties at room temperature, with a tensile strength of 875 MPa and a yield strength of 847 MPa. During tensile deformation, plastic strain primarily occurs through dislocation slip within the γ matrix and dislocation shear into the γ′ phase. Dislocations sheared into the γ′ phase exhibit distinct decomposition patterns. Microcracks initiate at γ′/γ interfaces where two slip systems intersect. As tensile loading continues, these microcracks coalesce, leading to increased local stress and unstable crack propagation along the γ/γ′ interfaces, ultimately resulting in fracture. This process constitutes the deformation and damage mechanism of the alloy during room-temperature tensile deformation. These findings suggest that high Re/Ru concentrations fundamentally alter low-temperature deformation pathways, which may improve resistance to brittle fracture during cold start or handling conditions. Full article

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17 pages, 2964 KB

Open AccessArticle

Synthesis, Structure, and Properties of the Complex Zintl Phase Eu₉Zn_4.5As₉: A Candidate Topological Insulator and Thermoelectric Material

by Spencer R. Watts, Olha Pokhvata, Thimira Kandabadage, Bhushan Thipe, Xiaojian Bai, Svilen Bobev and Sviatoslav Baranets

Crystals 2026, 16(2), 137; https://doi.org/10.3390/cryst16020137 - 13 Feb 2026

Cited by 1 | Viewed by 559

Abstract

Reported are the synthesis and detailed analysis of the crystal and electronic structure of the novel Zintl phase Eu₉Zn_4.5As₉. This material was identified in the densely populated Eu–Zn–As compositional space. For structure determination and for property measurements, [...] Read more.

Reported are the synthesis and detailed analysis of the crystal and electronic structure of the novel Zintl phase Eu₉Zn_4.5As₉. This material was identified in the densely populated Eu–Zn–As compositional space. For structure determination and for property measurements, suitable single crystals of this compound were grown from either Sn- or Pb-flux. Single-crystal X-ray diffraction methods indicate that Eu₉Zn_4.5As₉ crystallizes in the orthorhombic crystal system with the space group Pnma (a = 12.1953(7) Å, b = 4.3730(2) Å, c = 42.674(2) Å) and is formally isostructural to Ca₉Mn_4+xSb₉, the less common “9–4–9” type. The structure is heavily disordered, with multiple partially occupied sites, yet, according to the Zintl-Klemm formalism, a charge-balanced composition (Eu²⁺)₉(Zn²⁺)_4.5(As³⁻)₉ is attained. Electronic structure calculations for a model, disorder-free structure indicate no energy gap between the valence and the conduction bands and suggest (semi)metallic behavior. Preliminary susceptibility measurements confirm the expected divalent nature of Eu²⁺ ([Xe] 4f⁷ ground state). Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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21 pages, 5539 KB

Open AccessArticle

Study of 2-Benzylidene-1-indanone Derivatives as Electrodes

by María Elena Sánchez Vergara, Ricardo Ballinas-Indili, Naomi Itzel Medina Morales, Emilio Iván Sandoval Plata, Ruben A. Toscano and Cecilio Álvarez Toledano

Crystals 2026, 16(2), 136; https://doi.org/10.3390/cryst16020136 - 13 Feb 2026

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Abstract

In this work, indanone derivatives with a triphenylamine core structure (IND-1, IND-2, and IND-3) were studied as prospective electrodes. The indanones were synthesized and characterized for optimal deposition as charge-modulating electrodes. The structural arrangement of compound IND-3 was established, [...] Read more.

In this work, indanone derivatives with a triphenylamine core structure (IND-1, IND-2, and IND-3) were studied as prospective electrodes. The indanones were synthesized and characterized for optimal deposition as charge-modulating electrodes. The structural arrangement of compound IND-3 was established, and the structure crystallized in a P2₁/c monoclinic space group. The electrodes were evaluated for reflectance and band gaps of direct and indirect transitions. Indanones show optical band gap values in the range of 2.46 and 2.86 eV. These values were compared with those obtained theoretically by means of DFT, from which the HOMO and LUMO molecular orbitals were also calculated. To evaluate the indanone response, photoactive devices with indanone-derivative electrodes and copper phthalocyanine as a photoactive electrode were fabricated. Cyclic voltammetry (CV) was conducted using a two-electrode arrangement, within a potential range of −0.1 to 1 V, a step of 10 mV, and a scan rate of 0.1 V/s. The transported current is around 10⁻¹–10⁴ µA, and CV revealed distinct behaviors related to each kind of indanone. Finally, the electrodes were removed from each device and analyzed by IR spectroscopy, demonstrating that they did not undergo degradation during operation and can continue to be used for the manufacture of other devices. Full article

(This article belongs to the Special Issue Advances in Optoelectronic Materials)

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11 pages, 2501 KB

Open AccessArticle

The Desulfurization Ability of a High Al₂O₃ Type CaO-SiO₂-Al₂O₃-MgO-TiO₂ Blast Furnace Slag System at 1823 K

by Yongchun Guo, Mengyao Li and Zhimin Ding

Crystals 2026, 16(2), 135; https://doi.org/10.3390/cryst16020135 - 13 Feb 2026

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Abstract

In this study, CaO-SiO₂-Al₂O₃-MgO-TiO₂ slag was used as the research object to simulate the blast furnace ironmaking process. Based on the experimental data, the influences of basicity (R(w(CaO)/w(SiO₂))) [...] Read more.

In this study, CaO-SiO₂-Al₂O₃-MgO-TiO₂ slag was used as the research object to simulate the blast furnace ironmaking process. Based on the experimental data, the influences of basicity (R(w(CaO)/w(SiO₂))) and the magnesia–alumina ratio (w(MgO)/w(Al₂O₃)) on desulfurization ability are discussed. Additionally, the influences of dissimilarity, basicity, and the magnesia–alumina ratio on slag structure were analyzed using Fourier transform infrared spectroscopy (FT-IR). The results show that when w(Al₂O₃) = 20% and w(MgO)/w(Al₂O₃) = 0.50, sulfide capacity (lgC_s) accretion with the increment in R. Moreover, when w(Al₂O₃) = 20% and R = 1.30, sulfide capacity accretion with the increment in w(MgO)/w(Al₂O₃). Fourier transform infrared spectroscopy was used to confirm that, with increasing basicity and the magnesia–alumina ratio, the concentration of dissociated free oxygen ions (O²⁻) in slag increases, and these ions interact with the bridging oxygen (O⁰) of silicate to depolymerize the complex Si-O structure into simpler units. Full article

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

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44 pages, 17930 KB

Open AccessArticle

Synergistic Hf-rGO Reinforcement in Copper: A Pathway to Electrically Functional, Wear-Resistant Hybrid Composites

by Cevher Kürşat Macit, Bünyamin Aksakal, Merve Ayık, Turan Gurgenc and Yusuf Er

Crystals 2026, 16(2), 134; https://doi.org/10.3390/cryst16020134 - 12 Feb 2026

Cited by 1 | Viewed by 472

Abstract

Copper (Cu) is widely used in electrical and thermal management systems; however, its low hardness and limited dry sliding wear resistance reduce long-term reliability in friction-loaded conductive components. In this study, Cu–Hf and Cu–Hf–rGO hybrid composites were fabricated by powder metallurgy using 1.0–5.0 [...] Read more.

Copper (Cu) is widely used in electrical and thermal management systems; however, its low hardness and limited dry sliding wear resistance reduce long-term reliability in friction-loaded conductive components. In this study, Cu–Hf and Cu–Hf–rGO hybrid composites were fabricated by powder metallurgy using 1.0–5.0 wt.% Hf and 1.0–2.0 wt.% reduced graphene oxide (rGO). The microstructure and phase evolution were characterized by SEM/EDS and XRD. Electrical conductivity and hardness were measured, while tribological performance was evaluated by dry sliding wear tests based on mass loss. Post-wear surface characteristics were analyzed by AFM and LFM to assess nanoscale topography and frictional behavior. The hybrid composites exhibited composition-dependent multifunctional enhancements. Electrical conductivity increased from approximately 3.0 × 10⁶ S/m (~5.2% IACS) for pristine Cu to about 2.0 × 10⁷ S/m (~34.5% IACS) for the composite reinforced with 3.0 wt.% Hf and 2.0 wt.% rGO, indicating an optimum Hf–rGO combination that preserves continuous conductive pathways. Hardness increased from 60 ± 3 HV_0.30 to 159 ± 12 HV_0.30 for the composite containing 5.0 wt.% Hf and 2.0 wt.% rGO, demonstrating the dominant contribution of Hf to matrix strengthening and load-bearing capacity. The mass loss after 1000 m of sliding distance decreased from about 0.12 g for Cu to approximately 0.01 g for the 5.0 wt.% Hf–2.0 wt.% rGO hybrid composite, consistent with the concurrent increase in hardness and reduction in frictional shear during sliding. Nanoscale surface analyses revealed reduced surface roughness and frictional response, supporting the formation of a smoother and lower-friction sliding interface in rGO-containing composites. Overall, Hf enhanced load-bearing capacity through matrix strengthening, while rGO contributed to stabilizing conductive pathways and solid lubrication. Full article

(This article belongs to the Topic High Performance Ceramic Functional Materials)

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14 pages, 4009 KB

Open AccessArticle

Rational Design of α-MoO₃ Nanoflowers over Co₃O₄ Nanowire Arrays with Enhanced Active Site Exposure for High-Performance Water Oxidation

by Mrunal Bhosale, Aditya A. Patil and Chan-Wook Jeon

Crystals 2026, 16(2), 133; https://doi.org/10.3390/cryst16020133 - 12 Feb 2026

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Abstract

Developing effectual, stable, and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) remains pivotal for advancing sustainable hydrogen production via electrochemical water splitting. Herein, we report the rational design of Co₃O₄ nanowire arrays hierarchically decorated with α-MoO₃ nanoflowers (Co [...] Read more.

Developing effectual, stable, and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) remains pivotal for advancing sustainable hydrogen production via electrochemical water splitting. Herein, we report the rational design of Co₃O₄ nanowire arrays hierarchically decorated with α-MoO₃ nanoflowers (Co₃O₄@α-MoO₃) grown directly on nickel foam via a scalable hydrothermal strategy. By optimizing MoO₃ loading, the Co₃O₄@α-MoO₃-2 heterostructure achieves an ultralow overpotential of 209 mV at 10 mA cm⁻², a Tafel slope of 60 mV dec⁻¹, and superior charge-transfer kinetics in 1 M KOH. Comprehensive analysis reveals that the synergistic interfacial coupling enhances electronic conductivity, exposes abundant active sites (ECSA = 1106.50 cm²), and optimizes OER intermediate adsorption through mixed valence Co/Mo centers and oxygen defects. This work elucidates morphology–composition synergy in oxide heterostructures, offering a blueprint for high-performance OER electrocatalysts. Full article

(This article belongs to the Special Issue Advances in Electrocatalyst Materials)

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18 pages, 4287 KB

Open AccessArticle

Enhanced Dielectric Response and Electric Field-Sensing Properties of PDMS Composites by Graphene/Nitride Heterojunctions: Insights from Experiment and DFT

by Bo Li, Jiao Sun, Yuxing Lei, Tingting Jiang and Haitao Yang

Crystals 2026, 16(2), 132; https://doi.org/10.3390/cryst16020132 - 11 Feb 2026

Viewed by 424

Abstract

Flexible dielectric composite materials capable of converting power frequency electric fields into measurable electrical signals are of great significance in the field of non-contact electric field sensing in power systems. In this paper, graphene/nitride heterojunction powders were prepared using three representative nitrides (AlN, [...] Read more.

Flexible dielectric composite materials capable of converting power frequency electric fields into measurable electrical signals are of great significance in the field of non-contact electric field sensing in power systems. In this paper, graphene/nitride heterojunction powders were prepared using three representative nitrides (AlN, BN, and Si₃N₄) and embedded in polydimethylsiloxane (PDMS) to prepare flexible composite films with a fixed filler content of 5.0 wt%. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirmed the successful formation of the heterojunctions. The results showed that the nitride-related elements (Al, Si and N) were spatially correlated with the graphene-rich regions, thus providing abundant interfacial contact sites. Dielectric spectroscopy (50 Hz–50 kHz) showed that all samples exhibited typical dispersive behavior, with the real part of the dielectric constant decreasing monotonically with increasing frequency, and the loss tangent also decreasing smoothly. Under a 50 Hz parallel-plate electric field, the normalized induced voltage amplitude (PDMS = 1) increases to 1.070 (≈7.0%) for G/PDMS, and further to 1.0723–1.07447 (≈7.23–7.45%) for AlN–G/PDMS, BN–G/PDMS, and Si₃N₄-G/PDMS. DFT calculations confirm that the graphene/nitride interface has a stable structure with negative binding energies (−2.241, −1.773, and −3.062 eV for AlN–G, BN–G, and Si₃N₄–G, respectively). Significant charge redistribution and Mulliken charge transfer (0.0538, 0.2047, and 0.0244 eV, respectively) are present at the interface, accompanied by Fermi level density of states modulation and a small bandgap opening (~0.101 eV) in BN–G. These results collectively support the interfacial polarization-driven mechanism and provide a comparative basis for selecting nitride components in graphene-based heterojunction fillers in flexible dielectric electric field-sensing layers. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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22 pages, 16596 KB

Open AccessArticle

Thermal Stability of Cu/Zn-15Al-(Ni)/Al Joints: The Role of Ni-Refined Interfacial Layer in Retarding Phase Decomposition

by Tao Chen, Tengzhou Xu, Jingyi Luo, Peng He, Kai Meng, Siyi Chen, Wen Chen, Junyu Li and Rui Ji

Crystals 2026, 16(2), 131; https://doi.org/10.3390/cryst16020131 - 11 Feb 2026

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Abstract

Thermal degradation of the interfacial microstructure critically limits the service life of Zn-Al brazed Cu/Al joints. This work elucidates the stabilizing role of trace Ni (0.3 wt.%) in retarding interfacial deterioration during 200 °C isothermal aging for up to 1000 h. Microstructural evolution [...] Read more.

Thermal degradation of the interfacial microstructure critically limits the service life of Zn-Al brazed Cu/Al joints. This work elucidates the stabilizing role of trace Ni (0.3 wt.%) in retarding interfacial deterioration during 200 °C isothermal aging for up to 1000 h. Microstructural evolution and micromechanical responses were probed via SEM, EDS, and nanoindentation. In Ni-free joints, continuous Zn influx triggers the decomposition of the massive CuAl₂ phase into a defect-ridden, Zn-rich lamellar structure, precipitating a sharp decline in shear strength from 57 MPa to 37.5 MPa. Conversely, Ni doping constructs a robust fine-grained interfacial architecture. The Ni-bearing coral-like layer exhibits exceptional morphological stability, while the underlying Cu-based transition layer undergoes in situ stratification and Zn ejection, functioning as a chemical buffer to intercept Zn diffusion. This microstructural reconfiguration enables Ni-doped joints to sustain a shear strength of ~55.2 MPa after 1000 h—matching the initial strength of Ni-free counterparts. The superior durability stems from the modulus softening of the stratified transition layer and a multi-stage crack deflection mechanism, offering a viable metallurgical strategy for robust Cu/Al interconnects. Full article

(This article belongs to the Special Issue Surface Modification Treatments of Metallic Materials (2nd Edition))

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21 pages, 7415 KB

Open AccessArticle

Jadeite from Guatemala: New Observations and Distinctions Among Lavender and Black Jade

by Mengxi Zhao, Bo Xu, Siyi Zhao, Yining Liu and Zitong Li

Crystals 2026, 16(2), 130; https://doi.org/10.3390/cryst16020130 - 11 Feb 2026

Viewed by 663

Abstract

This study systematically investigates the mineralogical, spectral, and geochemical characteristics of Guatemalan lavender jadeite and black omphacite to elucidate their coloration mechanisms and genetic origins. Lavender samples are primarily composed of jadeite, which derives its color from synergistic effects involving Mn³⁺ and [...] Read more.

This study systematically investigates the mineralogical, spectral, and geochemical characteristics of Guatemalan lavender jadeite and black omphacite to elucidate their coloration mechanisms and genetic origins. Lavender samples are primarily composed of jadeite, which derives its color from synergistic effects involving Mn³⁺ and Fe²⁺-Ti⁴⁺ charge transfer (554–614 nm). In contrast, black samples are dominated by omphacite, which owes its dark hue to Cr³⁺ (670 nm) and Fe²⁺-Fe³⁺ charge transfer (857 nm). Chemically, lavender jadeite exhibits higher Na₂O and Al₂O₃, approaching the jadeite end-member composition, whereas black omphacite is enriched in CaO, MgO, and FeO. Trace element analyses reveal low overall abundances, with black omphacite showing synchronous LREE and HREE depletion forming a “bulge-shaped” pattern, while lavender jadeite displays N-MORB-like REE distributions. Guatemalan jadeites are distinguished from Myanmar counterparts by Y enrichment. The identification of graphite and CH₄ and CO₂ fluid inclusions indicates formation in an organic-rich reducing environment. Cathodoluminescence zoning and abundant fluid inclusions support a direct crystallization genesis from high-pressure fluids (P-type) in subduction zones. This study establishes key constraints for origin discrimination and genetic classification of Guatemalan lavender jadeite and black omphacite. Full article

(This article belongs to the Special Issue Modern Gem Crystals: Synthesis, Characterization, Genesis and Intelligent Analysis)

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18 pages, 3168 KB

Open AccessArticle

Au–NiZn/Ti Electrocatalyst for Efficient Sodium Borohydride Oxidation

by Tripura Ganti, Aldona Balčiūnaitė, Huma Amber, Giedrius Stalnionis, Jūratė Vaičiūnienė, Loreta Tamašauskaitė-Tamašiūnaitė and Eugenijus Norkus

Crystals 2026, 16(2), 129; https://doi.org/10.3390/cryst16020129 - 10 Feb 2026

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Abstract

Direct borohydride fuel cells (DBFCs) are emerging as a promising source of clean energy; however, their performance depends heavily on efficient anode catalysts for the oxidation reaction of sodium borohydride (BOR). In this study, we developed and tested the Au–NiZn/Ti electrocatalyst designed to [...] Read more.

Direct borohydride fuel cells (DBFCs) are emerging as a promising source of clean energy; however, their performance depends heavily on efficient anode catalysts for the oxidation reaction of sodium borohydride (BOR). In this study, we developed and tested the Au–NiZn/Ti electrocatalyst designed to improve the performance of DBFCs. Electrodeposition and alkaline leaching were utilized to transform a zinc-rich nickel coating into a porous dendritic structure on a titanium substrate. By adding a small amount of gold crystallites through galvanic displacement, the surface roughness and the number of active sites available for the reaction were significantly increased. Electrochemical tests confirmed that this modification enhances BOR and effectively suppresses unwanted side reactions like hydrogen evolution. The resulting catalyst demonstrated high stability, maintaining over 88% of its current density during extended operation. Ultimately, the study positions this gold-modified material as a cost-effective and durable solution for clean energy conversion technologies. Full article

(This article belongs to the Special Issue Advances in Electrocatalyst Materials for Sustainable Applications)

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33 pages, 3782 KB

Open AccessReview

Photocatalytic Reduction of CO₂ by Bi-Based Semiconductor: A Review on Recent Progress

by Yuming Lu, Jingkai Yan, Wei He, He Guo, Feng Liu, Zhenghua Yang and Wenxin Hu

Crystals 2026, 16(2), 128; https://doi.org/10.3390/cryst16020128 - 9 Feb 2026

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Abstract

Photocatalytic reduction of CO₂ into valuable solar fuels represents a promising strategy to address both energy crises and carbon emissions. Bismuth-based semiconductors have emerged as attractive visible-light-driven photocatalysts due to their suitable band structures, layered architectures, and tunable morphologies. This review systematically [...] Read more.

Photocatalytic reduction of CO₂ into valuable solar fuels represents a promising strategy to address both energy crises and carbon emissions. Bismuth-based semiconductors have emerged as attractive visible-light-driven photocatalysts due to their suitable band structures, layered architectures, and tunable morphologies. This review systematically summarizes recent advances in Bi-based photocatalysts for CO₂ photoreduction. First, the fundamental principles and key challenges of CO₂ photoreduction are outlined. Subsequently, the structural and electronic characteristics of typical Bi-based materials, including Bi₂O₃, Bi₂S₃, Bi₂MO₆ (M = W; Mo), BiVO₄, and BiOX (X = Cl; Br; I), are discussed. Emphasis is placed on design strategies to enhance photocatalytic performance, such as vacancy engineering, microstructure control, crystal facet engineering, heterojunction construction, cocatalyst loading, and their combinations. A comprehensive comparison of catalytic activities under various conditions is also provided. Finally, current limitations and future perspectives are highlighted, aiming to guide the rational design of efficient and stable Bi-based photocatalysts for CO₂ conversion. Full article

(This article belongs to the Special Issue Advances in Photocatalytic Technology and Materials)

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14 pages, 3488 KB

Open AccessArticle

Study on the IMC Growth Mechanism of Cu/Sn-58Bi/Cu Joint Under Electromigration with Alternating Current

by Bo Wang, Peiying Zhu, Guopei Zhang, Chunyuan Deng, Kaixuan He, Wei Huang and Kailin Pan

Crystals 2026, 16(2), 127; https://doi.org/10.3390/cryst16020127 - 9 Feb 2026

Viewed by 342

Abstract

With the ongoing miniaturization of solder joints in three-dimensional integrated electronic packaging, electromigration reliability has become a pressing concern. This study systematically examines the interfacial intermetallic compound (IMC) growth behavior of Cu/Sn-58Bi/Cu joint under electromigration (EM) with a symmetrical square-wave alternating current (AC). [...] Read more.

With the ongoing miniaturization of solder joints in three-dimensional integrated electronic packaging, electromigration reliability has become a pressing concern. This study systematically examines the interfacial intermetallic compound (IMC) growth behavior of Cu/Sn-58Bi/Cu joint under electromigration (EM) with a symmetrical square-wave alternating current (AC). Electron backscatter diffraction (EBSD) was employed to perform statistical spatial analysis of Sn grain orientations within the joints to reveal the growth mechanism of interfacial IMC. Results demonstrate that the AC field markedly enhances the anisotropy of IMC growth in Cu/Sn-58Bi/Cu joints, exhibiting two phenomena: uniform growth on both sides and rapid growth (polar growth) on one side of the interfacial IMC. Among them, the IMC thickness difference characterization quantity Δ_IMC reached as high as 45.56% for the latter. This is attributed to the directional regulation of atomic migration rate by Sn grain orientation (the angle θ between the c-axis and the electron flow) and is further amplified by the altered atomic diffusion pathways imposed by the Bi phase distribution. Specifically, the Sn grains exhibit a pronounced preferential orientation mode along the current path (horizontal direction), with an orientation gradient of 0.915 μm⁻¹. The arrangement of Bi-rich phases alters the distribution of Sn grains in Cu/Sn-58Bi/Cu joints, thereby reshaping the internal electron transport pathways and significantly intensifying the orientation-dependent effect of IMC growth. Moreover, Sn grains adjacent to the Bi-rich phase boundaries (phase boundary grains) display a stronger tendency for c-axis orientation parallel to the current direction, exhibiting an average effective orientation parameter 1.948 times greater than that of bulk grains, which establishes a well-defined spatial orientation gradient. Full article

(This article belongs to the Special Issue Recent Research on Electronic Materials and Packaging Technology)

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16 pages, 3744 KB

Open AccessArticle

Bio-Purines as Co-Formers in Resveratrol Amorphous Systems

by Yuhang Liu, Ziqing Wu, Fenghua Chen, Yongming Liu and Rongrong Xue

Crystals 2026, 16(2), 126; https://doi.org/10.3390/cryst16020126 - 9 Feb 2026

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Abstract

In the organic biomineralization of guanine (GUA), amorphous GUA is utilized to enhance its solubility, facilitating its transport for the formation of biominerals, and GUA nanocrystals are employed to protect tissues from ultraviolet damage. These principles of GUA biomineralization inspire us to improve [...] Read more.

In the organic biomineralization of guanine (GUA), amorphous GUA is utilized to enhance its solubility, facilitating its transport for the formation of biominerals, and GUA nanocrystals are employed to protect tissues from ultraviolet damage. These principles of GUA biomineralization inspire us to improve the solubility and photostability of trans-resveratrol (RES) using bio-purines, which limits its bioavailability. Bio-purines, such as GUA, hypoxanthine (HYP), and adenine (ADE), were used as co-formers in the amorphous systems of RES. Amorphous RES-2Purines with a 1:2 molar ratio were prepared via the neat ball-milling method and confirmed by powder X-ray diffraction, Raman spectroscopy, and diffuse reflectance spectroscopy. The stability, dissolution profiles, and photostability of RES-2Purines were comprehensively compared. RES-2Purines show high amorphous-to-crystalline transformation temperatures (>100 °C), confirmed by the differential scanning calorimetry-thermogravimetric analysis. Both RES-2HYP and RES-2ADE show an enhanced RES solubility (about 1.6-fold that of raw RES) in water and the simulated gastric fluid (pH 1.2). RES-2Purines can recrystallize quickly after being dispersed in water, which limits the solubility enhancements of RES-2Purines. RES-2Purines have better photostability than raw RES. Bio-purines are promising co-formers for amorphous systems to enhance the solubility and photostability of poorly water-soluble compounds. Full article

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18 pages, 11347 KB

Open AccessArticle

Kinetics of Oxidation at High Temperature and Degradation States of Cr-Free Al-Containing Cobalt and Nickel Alloys Reinforced by TaC Carbides

by Patrice Berthod

Crystals 2026, 16(2), 125; https://doi.org/10.3390/cryst16020125 - 8 Feb 2026

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Abstract

Two cobalt alloys and one nickel alloy, containing Ta and C in similar atomic contents and either 5 or 10 wt.% Al, were cast. Their microstructures and their oxidation behaviors in air at 1200 °C over 50 h were investigated. All contained eutectic [...] Read more.

Two cobalt alloys and one nickel alloy, containing Ta and C in similar atomic contents and either 5 or 10 wt.% Al, were cast. Their microstructures and their oxidation behaviors in air at 1200 °C over 50 h were investigated. All contained eutectic script-like TaC carbides and a dendritic matrix which was either single-phased (FCC) or double-phased (FCC + Co₃Al). The cobalt sample with 5 wt.% oxidized catastrophically, became thinner, lost all its TaC, and was covered by a thick oxide shell (outer CoO and inner mixture of CoO, CoAl₂O₄ and Ta-rich oxides). The two other alloys, Ni-based with 5 wt.% Al and Co-based with 10 wt.% Al, oxidized more slowly, with a mass gain kinetic slightly lower than that for chromia-forming alloys at 1200 °C and a continuous duplex oxide scale made of an outer MAl₂O₄ spinel and inner Al₂O₃ scales. This evidences the existence of two Al content thresholds, depending on the base element, that must be exceeded to obtain acceptable oxidation behavior. Full article

(This article belongs to the Special Issue Microstructure Characterization and Design of Advanced Alloys)

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22 pages, 12196 KB

Open AccessArticle

Silver-Based Nanoparticles as Antibacterial Materials

by Adriana-Gabriela Schiopu, Mihai Oproescu, Sorin Georgian Moga, Ecaterina Magdalena Modan, Denis Aurelian Negrea, Daniela Istrate, Georgian Vasile Bîrsan and Marian Catalin Ducu

Crystals 2026, 16(2), 124; https://doi.org/10.3390/cryst16020124 - 8 Feb 2026

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Abstract

This study investigates the elaboration, structural characteristics, and antibacterial performance of silver-based nanoparticles obtained via a hydrolytic chemical route, with and without assistance from ultrasound and microwave irradiation. Two silver nitrate precursor concentrations (1 M and 2 M) were employed to evaluate the [...] Read more.

This study investigates the elaboration, structural characteristics, and antibacterial performance of silver-based nanoparticles obtained via a hydrolytic chemical route, with and without assistance from ultrasound and microwave irradiation. Two silver nitrate precursor concentrations (1 M and 2 M) were employed to evaluate the influence of synthesis conditions on phase composition, morphology, and antimicrobial efficiency. The obtained powders were characterized by ATR-FTIR, X-ray diffraction (XRD), and scanning electron microscopy (SEM). XRD analysis revealed that drying at 120 °C led to oxide-rich systems dominated by Ag₂O, with minor contributions from metallic Ag and carbonate species, while calcination at 550 °C resulted in complete phase transformation into highly crystalline metallic silver. SEM observations demonstrated that precursor concentration and synthesis assistance strongly affect particle size, aggregation degree, and surface morphology. Ultrasound- and microwave-assisted synthesis promoted finer crystallite sizes and more homogeneous particle distributions compared to non-assisted routes. The antibacterial activity was evaluated against Escherichia coli (Gram-negative) and Clostridium perfringens (Gram-positive, anaerobic, spore-forming). Oxide-rich samples, particularly Ox.Ag/2 M, exhibited rapid and complete bacterial inactivation within 30 min, while metallic silver samples showed time-dependent antibacterial behavior, achieving full inhibition after 4 h. The results demonstrate that antibacterial efficiency is governed by a synergistic interplay between silver oxidation state, nanoscale morphology, and surface reactivity. These findings highlight the potential of tailored silver-based nanomaterials as effective antibacterial materials for biomedical, food safety, and environmental applications. Full article

(This article belongs to the Special Issue Emerging Nanostructured Powders: Synthesis and Applications)

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