Journal Description
Crystals
Crystals
is an international, peer-reviewed, open access journal on Crystallography published monthly online by MDPI. The Professional Committee of Key Materials and Technology for Electronic Components (PC-KMTEC) is affiliated with Crystals and its members receive discounts on the article processing charges.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
- Journal Rank: JCR - Q2 (Crystallography) / CiteScore - Q2 (Condensed Matter Physics)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 10.6 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Impact Factor:
2.7 (2022);
5-Year Impact Factor:
2.6 (2022)
Latest Articles
Effect of Erbium Micro-Additions on Microstructures and Properties of 2024 Aluminum Alloy Prepared by Microwave Sintering
Crystals 2024, 14(4), 382; https://doi.org/10.3390/cryst14040382 (registering DOI) - 19 Apr 2024
Abstract
The effects of rare earth erbium (Er) micro-additions on the microstructures and mechanical properties of 2024 aluminum alloy were investigated. The microstructures and fracture surfaces of specimens prepared via high-energy ball milling, cold isostatic pressing and microwave sintering were carried out by optical
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The effects of rare earth erbium (Er) micro-additions on the microstructures and mechanical properties of 2024 aluminum alloy were investigated. The microstructures and fracture surfaces of specimens prepared via high-energy ball milling, cold isostatic pressing and microwave sintering were carried out by optical microscopy (OM) and scanning electron microscopy (SEM). Under the conditions of sintering heating rate of 20 min/°C and soaking time of 30 min at 490 °C, it was found that with the increase in Er addition, the grain size first decreased then increased, and it reached a minimum size of about 5 μm when the Er content was 0.6%, showing that the grains were refined. At the same time, the compactness and microhardness reached maximum levels, which were 97.6% and 94.5 HV, respectively. Moreover, the tensile strength and elongation reached the peak at 160.5 MPa and 4.4%, respectively. The dynamic mechanical response of Er/2024Al alloy with different Er content was studied through a split Hopkinson pressure bar (SHPB) at strain rates of 600 s−1 and 800 s−1, respectively. Both at the strain rates of 600 s−1 and 800 s−1, the dynamic yield stress of the specimens increased gradually with an increase in Er content. For the 0.6 wt.% Er specimen, the dynamic yield stress reached 371.3 MPa at a strain rate of 800 s−1, which was 28.2% higher than that at a strain rate of 600 s−1. When the strain rate is 800 s−1, the deformation degree of the 0.6 wt.%Er specimen is 55.3%, which is 14.7% higher than for the Er-free one, and there are adiabatic shear bands formed in the 0.6 wt.%Er specimen. Through a fracture analysis of the samples, a certain number of dimples appeared in the fracture of an impact specimen, indicating that the addition of Er improved the toughness of the material. This research can provide a reference for the development and application of high-performance aluminum alloy in automotive structural materials.
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(This article belongs to the Special Issue Crystallization of High Performance Metallic Materials (II))
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Adsorption of Ni(II) from Aqueous Media on Biodegradable Natural Polymers—Sarkanda Grass Lignin
by
Elena Ungureanu, Costel Samuil, Denis C. Țopa, Ovidiu C. Ungureanu, Bogdan-Marian Tofanică, Maria E. Fortună and Carmen O. Brezuleanu
Crystals 2024, 14(4), 381; https://doi.org/10.3390/cryst14040381 - 18 Apr 2024
Abstract
Heavy metals are pollutants that pose a risk to living systems due to their high toxicity and ability to accumulate and contaminate. This study proposes an alternative approach to the static adsorption of Ni(II) from aqueous media using Sarkanda grass lignin crystals, the
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Heavy metals are pollutants that pose a risk to living systems due to their high toxicity and ability to accumulate and contaminate. This study proposes an alternative approach to the static adsorption of Ni(II) from aqueous media using Sarkanda grass lignin crystals, the non-cellulosic aromatic component of biomass, as an adsorbent substrate. To determine the best experimental conditions, we conducted tests on several parameters, including the initial and adsorbent solution pH, the concentration of Ni(II) in the aqueous solution, the amount of adsorbent used, and the contact time at the interface. The lignin’s adsorption capacity was evaluated using the Freundlich and Langmuir models to establish equilibrium conditions. The Lagergren I and Ho–McKay II kinetic models were used to determine the adsorption mechanism based on surface analyses and biological parameters such as the number of germinated seeds, energy, and germination capacity in wheat caryopses (variety Glosa) incorporated in the contaminated lignin and in the filtrates resulting from phase separation. The results suggest that Sarkanda grass lignin is effective in adsorbing Ni(II) from aqueous media, particularly in terms of adsorbent/adsorbate dosage and interfacial contact time.
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(This article belongs to the Special Issue Photocatalysis and Targeted Sorbent Activity of Advanced Polymer-Based Composites)
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The Influence of In3+ on the Crystal Growth and Visible Band Photorefraction of Uranium-Doped Lithium Niobate Single Crystals
by
Tian Tian, Wenjie Xu, Chenkai Fang, Yuheng Chen, Hongde Liu, Yaoqing Chu, Hui Shen and Jiayue Xu
Crystals 2024, 14(4), 380; https://doi.org/10.3390/cryst14040380 - 18 Apr 2024
Abstract
A series of lithium niobate crystals co-doped with uranium and indium was successfully grown by the modified vertical Bridgman method for the first time. With increasing In3+ ion doping concentration, the segregation coefficient of uranium and indium progressively deviated from 1. The
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A series of lithium niobate crystals co-doped with uranium and indium was successfully grown by the modified vertical Bridgman method for the first time. With increasing In3+ ion doping concentration, the segregation coefficient of uranium and indium progressively deviated from 1. The structural refinement indicated that uranium ions with high valence preferred to occupy the Nb sites in LN: In, U crystals. LN: In2.0, U0.6 achieved multi-wavelength holographic writing with diffraction efficiency comparable to commercial crystals LN:Fe0.3, demonstrating a response time that was four times shorter than LN:Fe0.3. XPS analysis was employed to investigate the valence states of In3+ ions in LN: In2.0, U0.6, in which uranium ions presented three valences of +4, +5 and +6. Furthermore, the ‘real threshold concentration’ of In3+ ions in LN: In, U was calculated using the Li-vacancy model, which is consistent with the results obtained from the experimental study of the OH- absorption spectrum. Discussions on the photorefractive centers in LN: In, U are also provided. This study not only demonstrates the impact of doping In3+ ions on the growth of LN:U crystals, but also offers new insights into the photorefractive properties of LN in the visible band.
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(This article belongs to the Special Issue Advances in Crystal Growth: Pioneering Materials for Tomorrow's Technologies)
Open AccessArticle
Study on the Synthesis of LTA-Type Molecular Sieves from Coal Gangue and Aluminum Ash and Its Adsorption Properties towards Cu2+
by
Qingping Wang, Wei Xu, Jingyi Cai, Qingbo Yu and Jing Min
Crystals 2024, 14(4), 379; https://doi.org/10.3390/cryst14040379 (registering DOI) - 18 Apr 2024
Abstract
Coal gangue and aluminum ash emerge as quintessential constituents within the ambit of coal-derived solid waste and industrial residue, respectively. Leveraging coal gangue as a primary substrate and aluminum ash as an adjunct aluminum source, molecular sieves can be synthesized through hydrothermal means.
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Coal gangue and aluminum ash emerge as quintessential constituents within the ambit of coal-derived solid waste and industrial residue, respectively. Leveraging coal gangue as a primary substrate and aluminum ash as an adjunct aluminum source, molecular sieves can be synthesized through hydrothermal means. By modulating the dosage of aluminum ash, molecular sieves with varying crystalline structures can be obtained. The synthesized LTA-type molecular sieves manifest in two distinct morphologies: regular tetrahedral and stratified spherical stacking, evincing commendable Cu2+ adsorption efficacy. The Cu2+ adsorption phenomenon predominantly transpires via chemisorption, albeit with ancillary manifestations of physical adsorption. The valorization of coal gangue and aluminum ash towards the synthesis of molecular sieves not only underscores the elevation of industrial solid waste towards high-value utility, but also underscores the praxis of waste remediation through upcycling.
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(This article belongs to the Section Hybrid and Composite Crystalline Materials)
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Crystallization of Secondary Phase on Super-Duplex Stainless Steel SAF2507: Advanced Li-Ion Battery Case Materials
by
Byung-Hyun Shin, Dohyung Kim and Jang-Hee Yoon
Crystals 2024, 14(4), 378; https://doi.org/10.3390/cryst14040378 - 18 Apr 2024
Abstract
The demand for Li-ion batteries has increased because of their extensive use in vehicles and portable electronic devices. This increasing demand implies greater interaction between batteries and humans, making safety a paramount concern. Although traditional batteries are fabricated using Al, recent efforts to
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The demand for Li-ion batteries has increased because of their extensive use in vehicles and portable electronic devices. This increasing demand implies greater interaction between batteries and humans, making safety a paramount concern. Although traditional batteries are fabricated using Al, recent efforts to enhance safety have led to the adoption of AISI304. The strength and corrosion resistance of AISI304 are greater than those of Al; however, issues such as stress-induced phase transformation and low high-temperature strength have been observed during processing. Duplex stainless steel SAF2507, which is characterized by a dual-phase structure consisting of austenite and ferrite, exhibits excellent strength and corrosion resistance. Although SAF2507 demonstrated outstanding high-temperature strength up to 700 °C, it precipitated a secondary phase. The precipitation of this secondary phase, believed to be caused by the precipitation of the carbides of Cr and Mo, has been extensively studied. Research on the precipitation of the secondary phase near 1000 °C has been conducted owing to the annealing temperature (1100 °C) of the SAF2507 solution. The secondary phase precipitates at approximately 1000 °C because of slow cooling rates. However, few studies have been conducted on the precipitation of the secondary phase at approximately 700 °C. This study analyzed the precipitation behavior of the secondary phase at 700 °C when SAF2507 was applied and assessed its safety during heat generation in Li-ion batteries. The precipitation behavior was analyzed using field emission scanning electron microscopy for morphology, energy-dispersive X-ray spectroscopy for composition, and X-ray diffraction for phase identification.
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(This article belongs to the Special Issue Advanced Crystalline Materials, Mechanical Properties and Innovative Production Systems (2nd Edition))
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Numerical Analysis of a High-Pressure Spatial Chemical Vapor Deposition (HPS-CVD) Reactor for Flow Stability at High Pressures
by
Hooman Enayati and Siddha Pimputkar
Crystals 2024, 14(4), 377; https://doi.org/10.3390/cryst14040377 - 18 Apr 2024
Abstract
Highly indium-rich group-III nitrides are attracting attention for advancing our capacity to create highly effective optical emitters at extended visible/IR wavelengths or for enhancing bandgap engineering possibilities within the group-III nitride material framework. Current methods of synthesis are constrained in their efficacy, partially
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Highly indium-rich group-III nitrides are attracting attention for advancing our capacity to create highly effective optical emitters at extended visible/IR wavelengths or for enhancing bandgap engineering possibilities within the group-III nitride material framework. Current methods of synthesis are constrained in their efficacy, partially owing to the low decomposition temperature of indium nitride. Implementation of a new design of a vertical high-pressure spatial chemical vapor deposition (HPS-CVD) reactor with six separated precursor source zones and a rotating wafer carrier disk carrying four 2-inch wafers is proposed and analyzed using COMSOL Multiphysics as a commercial computational fluid dynamics (CFD) program to study the fluid phenomena inside the numerical domain. This study focuses on understanding the different flow patterns within the chambers at super-atmospheric conditions (5 atm to 30 atm) and identifying suitable operating conditions under which smooth and dominant vortex-free flow is achieved. Four 2-inch wafers are heated to maintain a temperature of 1200–1300 K at each pressure and gas type. Three different gas types (nitrogen, hydrogen, and ammonia) are used, and the impacts of different inlet flow velocities and rotational speeds are investigated and discussed. An operating matrix is presented for each analyzed system pressure providing suitable combinations of these operational variables for smooth flow in the chambers. Each gas type was identified to have a range of suitable rotational and inlet velocity regimes at each operating pressure. Overlap of these three gas-specific operating condition windows resulted in the identification of a generally suitable operating condition for smooth flow patterns in the system regardless of the gas type used, as required for the growth of group-III nitride materials.
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(This article belongs to the Section Materials for Energy Applications)
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Controlled Crystallization of Hybrid Perovskite Films from Solution Using Prepared Crystal Centers
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Vyacheslav Moshnikov, Ekaterina Muratova, Andrey Aleshin, Alexandr Maksimov, Gregory Nenashev, Igor Vrublevsky, Nikita Lushpa, Alexandr Tuchkovsky, Anton Zhilenkov and Olga Kichigina
Crystals 2024, 14(4), 376; https://doi.org/10.3390/cryst14040376 - 18 Apr 2024
Abstract
The crystallization conditions from the solution play an important role in determining the morphology, phase composition, and photovoltaic properties of perovskite films. Post-processing of the obtained films can have a crucial role in increasing the grain size of perovskite and enhancing its crystallinity.
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The crystallization conditions from the solution play an important role in determining the morphology, phase composition, and photovoltaic properties of perovskite films. Post-processing of the obtained films can have a crucial role in increasing the grain size of perovskite and enhancing its crystallinity. It has been shown that the formation of crystal nuclei can be utilized to accelerate crystallization. In this case, crystallization occurs through the growth of seed crystals created in the solution, enabling the formation of relatively large crystals. For the deposition of CH3NH3PbI3 hybrid halide perovskite films from a solution of the perovskite in dimethylformamide, the spin coating technique was employed. Pre-crystallization was achieved by annealing the films at a temperature of 100 or 110 °C. The dissolution process involved adding a drop of dimethylformamide onto the substrate surface and allowing it to partially dissolve the perovskite film. Subsequently, residual solvent was removed through spin coating. The morphological analysis of the perovskite film surface after recrystallization at temperatures ranging from 80 to 130 °C was performed. The infrared transmission spectra of the obtained perovskite films were investigated, and their light absorption characteristics were studied through transmission spectra. The perovskite structure in the obtained films was confirmed by the peaks observed in the X-ray diffraction patterns. It has been shown that the photocurrent values for solar cells with perovskite films obtained by recrystallization are 15–20% higher than those of perovskite films obtained by traditional crystallization methods.
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(This article belongs to the Section Materials for Energy Applications)
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Competing Magnetocrystalline and Shape Anisotropy in Thin Nanoparticles
by
Dominika Kuźma, Oleksandr Pastukh and Piotr Zieliński
Crystals 2024, 14(4), 375; https://doi.org/10.3390/cryst14040375 - 17 Apr 2024
Abstract
Micromagnetic computations were performed to predict the magnetisation maps in thin elliptically shaped nanoparticles under a variable external magnetic field. Two materials were compared as the constituents of the nanoparticles: permalloy as an example of an isotropic magnet and cobalt, i.e., a hard
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Micromagnetic computations were performed to predict the magnetisation maps in thin elliptically shaped nanoparticles under a variable external magnetic field. Two materials were compared as the constituents of the nanoparticles: permalloy as an example of an isotropic magnet and cobalt, i.e., a hard magnetic material marked with a single easy axis. The interplay of the shape and magnetocrystalline anisotropy gives rise to a variety of switching scenarios, which may be of interest in designing memory storage devices. A fairly periodic shape-induced superlattice-like spin configuration occurs when the shape and magnetocrystalline easy axes are orthogonal. Possible applications as magnonic devices are discussed.
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(This article belongs to the Special Issue Recent Advances and Applications of Nanomaterials)
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Mechanochemical Synthesis of Praziquantel Hemihydrate in the Presence of Five Solvents with Different Water Miscibility
by
Ilenia D’Abbrunzo, Dario Voinovich and Beatrice Perissutti
Crystals 2024, 14(4), 374; https://doi.org/10.3390/cryst14040374 - 16 Apr 2024
Abstract
In this study, we report the mechanochemical synthesis of praziquantel hemihydrate in the presence of five solvents with different water miscibility. The commercially available praziquantel Form A (a racemic anhydrate structure) was ground in the presence of several water–solvent mixtures using two grinding
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In this study, we report the mechanochemical synthesis of praziquantel hemihydrate in the presence of five solvents with different water miscibility. The commercially available praziquantel Form A (a racemic anhydrate structure) was ground in the presence of several water–solvent mixtures using two grinding procedures (i.e., direct liquid-assisted grinding and neat grinding plus liquid-assisted grinding). Five organic solvents (i.e., acetic acid, 2-pyrrolidone, ethanol, ethyl acetate and hexane) were chosen considering their different miscibility with water and their capability to form solvates with praziquantel (documented for acetic acid and 2-pyrrolidone). The results suggested that the use of a second solvent has a detrimental effect on the formation of the hemihydrate. The inclusion of water in the solid is even worse in the case of water-miscible solvents, probably due to the favored interactions between the liquids. In fact, hexane is the only solvent permitting the mechanochemical crystallization of praziquantel hemihydrate to a limited extent. Importantly, interconversion studies between the hydrate/monosolvate/anhydrous forms revealed a preferential inclusion of solvents over water in the crystal lattice when using acetic acid or 2-pyrrolidone and complete dehydration of the hemihydrate and conversion in the most thermodynamically stable polymorph A of praziquantel with ethanol, ethyl acetate and hexane.
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(This article belongs to the Special Issue Structural Studies in Drug Discovery and Development: From the Lead to the Pharmaceutical Form)
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Improved Joint Formation and Ductility during Electron-Beam Welding of Ti6Al4V and Al6082-T6 Dissimilar Alloys
by
Georgi Kotlarski, Darina Kaisheva, Maria Ormanova, Borislav Stoyanov, Vladimir Dunchev, Angel Anchev and Stefan Valkov
Crystals 2024, 14(4), 373; https://doi.org/10.3390/cryst14040373 - 16 Apr 2024
Abstract
The current work is based on investigating the influence of different technological conditions of electron-beam welding on the microstructure and mechanical properties of joints between Ti6Al4V and Al6082-T6 dissimilar alloys. The plates were in all cases preheated to 300 °C. Different strategies of
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The current work is based on investigating the influence of different technological conditions of electron-beam welding on the microstructure and mechanical properties of joints between Ti6Al4V and Al6082-T6 dissimilar alloys. The plates were in all cases preheated to 300 °C. Different strategies of welding were investigated such as varying the electron-beam current/welding speed ratio (Ib/vw) and applying a beam offset towards the aluminum side. The heat input during the experiments was varied in order to guarantee full penetration of the electron beam. The macrostructure of the samples was studied, and the results indicated that using a high beam power and a high welding speed leads to an increased formation of defects within the structure of the weld seam. Utilizing a lower beam current along with a lower welding speed leads to the stabilization of the electron-beam welding process and thus to the formation of an even weld seam with next to no defects and high ductility. Using this approach gave the highest ultimate tensile strength (UTS) of 165 MPa along with a yield strength (YS) of 80 MPa and an elongation (ε) figure of 18.4%. During the investigation, improved technological conditions of electron-beam welding of Ti6Al4V and Al6082-T6 dissimilar alloys were obtained, and the results were discussed regarding possible practical applications of the suggested approach along with its scientific contribution to developing further strategies for electron-beam welding of other dissimilar alloys. The downsides and the economic effect of the presented method for welding Ti6Al4V and Al6082-T6 were also discussed.
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(This article belongs to the Special Issue Advanced Crystalline Materials, Mechanical Properties and Innovative Production Systems (2nd Edition))
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New Insight into the Electronic and Magnetic Properties of Sub-Stoichiometric WO3: A Theoretical Perspective
by
Mario Italo Trioni, Fausto Cargnoni, Stefano Americo and Raffaella Soave
Crystals 2024, 14(4), 372; https://doi.org/10.3390/cryst14040372 - 16 Apr 2024
Abstract
We present a theoretical investigation on the wide-band-gap semiconductor WO in its room-temperature monoclinic structure. We carried out density functional theory and GGA-1/2 calculations on the bulk phase and the most stable (001) surface of the material, either in their stoichiometric
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We present a theoretical investigation on the wide-band-gap semiconductor WO in its room-temperature monoclinic structure. We carried out density functional theory and GGA-1/2 calculations on the bulk phase and the most stable (001) surface of the material, either in their stoichiometric form or in the presence of oxygen vacancies at various concentrations. Concerning the bulk phase, our results show how the inclusion of these defects correctly reproduces the intrinsic n-type doping of the material. The system is also found to be magnetic at reasonably high defect concentrations. As for the surface, the presence of vacancies gives rise to a magnetic behavior, whose features depend on the relative arrangement of native point defects. Oxygen vacancies are also responsible for additional tungsten oxidation states in both bulk and surface. Based on these results, we provide a rationale for the interpretation of most experimental data of this material and, possibly, other widespread transition metal oxides with similar properties and applications such as ReO , TiO , and SnO .
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(This article belongs to the Special Issue Emergent Properties in Strongly Correlated Materials)
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Study of AlN Epitaxial Growth on Si (111) Substrate Using Pulsed Metal–Organic Chemical Vapour Deposition
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Muhammad Iznul Hisyam, Ahmad Shuhaimi, Rizuan Norhaniza, Marwan Mansor, Adam Williams and Mohd Rofei Mat Hussin
Crystals 2024, 14(4), 371; https://doi.org/10.3390/cryst14040371 - 16 Apr 2024
Abstract
A dense and smooth aluminium nitride thin film grown on a silicon (111) substrates using pulsed metal–organic chemical vapor deposition is presented. The influence of the pulsed cycle numbers on the surface morphology and crystalline quality of the aluminium nitride films are discussed
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A dense and smooth aluminium nitride thin film grown on a silicon (111) substrates using pulsed metal–organic chemical vapor deposition is presented. The influence of the pulsed cycle numbers on the surface morphology and crystalline quality of the aluminium nitride films are discussed in detail. It was found that 70 cycle numbers produced the most optimized aluminium nitride films. Field emission scanning electron microscopy and atomic force microscopy images show a dense and smooth morphology with a root-mean-square-roughness of 2.13 nm. The narrowest FWHM of the X-ray rocking curve for the AlN 0002 and 10–12 reflections are 2756 arcsec and 3450 arcsec, respectively. Furthermore, reciprocal space mapping reveals an in-plane tensile strain of 0.28%, which was induced by the heteroepitaxial growth on the silicon (111) substrate. This work provides an alternative approach to grow aluminium nitride for possible application in optoelectronic and power devices.
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(This article belongs to the Special Issue Epitaxial Growth and Application of Metallic Oxide Thin Films)
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Site Occupancy Preference and Magnetic Properties in Nd2(Fe,Co)14B
by
Xubo Liu and Ikenna C. Nlebedim
Crystals 2024, 14(4), 370; https://doi.org/10.3390/cryst14040370 - 16 Apr 2024
Abstract
Partial replacement of Fe by Co is an effective method to increase Curie temperature (TC), which improves the thermal stability of magnetic properties in Nd2Fe14B-based permanent magnets. The correlation between Fe substitution and magnetic properties has
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Partial replacement of Fe by Co is an effective method to increase Curie temperature (TC), which improves the thermal stability of magnetic properties in Nd2Fe14B-based permanent magnets. The correlation between Fe substitution and magnetic properties has been studied in Nd2(Fe,Co)14B via a first-principles calculation. The calculated Fe substitution energies indicate that the Co atoms avoid the 8j2 site, which agrees with the experiments. The Co atoms are ferromagnetically coupled with Fe sublattice and show magnetic moments of about 1.2 to 1.7 μB at different crystallographic sites, less than that of Fe (2.1–2.7 μB), resulting in the decrease in total magnetization at ground state (0 K) with increasing Co content. The effective exchange interaction parameter, derived from the energy difference between varied magnetic structures, increases from 7.8 meV to 17.0 meV with increasing Co content from x = 0 to x = 14 in Nd2Fe14−xCoxB. This change in the effective exchange interaction parameter is responsible for the enhancement of TC in Nd2(Fe,Co)14B. The total magnetization at 300 K, derived from mean-field theory, shows a peak maximum value at x = 1 in Nd2Fe14−xCoxB. The phenomenon results from the interplay between the reduction of the magnetic moment in the Fe(Co) sublattice and the enhancement of TC with increasing Co content.
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(This article belongs to the Special Issue First Principles Calculation for Crystalline Materials)
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Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers
by
Iker Lorenzo-Feijoo, Aida Serrano, Cayetano Hernández-Gómez, José Luis F. Cuñado and Pilar Prieto
Crystals 2024, 14(4), 369; https://doi.org/10.3390/cryst14040369 - 16 Apr 2024
Abstract
Antiferromagnetic/ferromagnetic (AF/F) systems have been extensively investigated due to the importance that interfacial exchange coupling effects have in the development of magnetic storage technologies. Recently, these systems have garnered interest for the potential they have to imprint the magnetic moments of the AF
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Antiferromagnetic/ferromagnetic (AF/F) systems have been extensively investigated due to the importance that interfacial exchange coupling effects have in the development of magnetic storage technologies. Recently, these systems have garnered interest for the potential they have to imprint the magnetic moments of the AF into an F layer, offering the possibility of using it as a read-out mechanism in antiferromagnetic spintronics. In this study, we explored the importance of crystalline orientation and strains induced by the substrate in the exchange coupling properties of NiO/FeCo AF/F bilayers. For that, we have grown NiO/FeCo bilayers on MgO (001) and Al2O3 (0001) substrates varying the FeCo layer thickness. In addition, we have analyzed both deposited samples and those with induced interfacial unidirectional anisotropy. For inducing such interfacial anisotropy, we used a field cooling procedure, heating the bilayers to 650 K and subsequently cooling down to room temperature under the presence of an external magnetic field of 300 mT. We have investigated the effect of the substrate in terms of crystalline orientation and lattice mismatching on the AF/F exchange coupling as well as the dependence of the coercivity and exchange bias on the inverse F layer thickness that is consistent with the interfacial origin of the AF/F exchange coupling. Moreover, the angular dependence of the magnetic properties was explored by using vectorial Kerr magnetometry, confirming the presence of both magnetocrystalline anisotropy, arising from the epitaxial character of the growing process mainly when the bilayer is grown on MgO (001) substrates, and the field cooling (FC)-induced unidirectional anisotropy.
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(This article belongs to the Section Crystal Engineering)
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The Impact of Temperature and Power Variation on the Optical, Wettability, and Anti-Icing Characteristics of AZO Coatings
by
Kamlesh V. Chauhan, Sushant Rawal, Nicky P. Patel and Vandan Vyas
Crystals 2024, 14(4), 368; https://doi.org/10.3390/cryst14040368 - 15 Apr 2024
Abstract
The structural, wettability, and optical characteristics of aluminum-doped zinc oxide (AZO) thin films were studied with the objective of understanding the impact of deposition power and deposition temperature. Thin films were deposited using a radio frequency (RF) magnetron sputtering technique. The power output
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The structural, wettability, and optical characteristics of aluminum-doped zinc oxide (AZO) thin films were studied with the objective of understanding the impact of deposition power and deposition temperature. Thin films were deposited using a radio frequency (RF) magnetron sputtering technique. The power output of the RF was augmented from 200 to 260 W, and the temperature was increased from 50 to 200 °C, which led to the development of a (002) peak for zinc oxide. The study of film thickness was carried out using the Swanepoel envelope method from data obtained through the UV-Vis spectrum. An increase in surface roughness value was shown to be connected with fluctuations in temperature as well as increases in deposition power. The findings revealed that as deposition power and temperature increased, the value of optical transmittance decreased, ranging from 70% to 90% based on the deposition parameters within the range of wavelengths that extend from 300 to 800 nm. The wettability properties of the samples were studied, and the maximum contact angle achieved was 110°. A Peltier apparatus was utilised in order to investigate the anti-icing capabilities, which revealed that the icing process was slowed down 3.38-fold. This work extends the understanding of the hydrophobicity and anti-icing capabilities of AZO thin films, specifically increasing both attributes which provide feasible options for purposes requiring resistance to ice.
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(This article belongs to the Special Issue Metal Oxides: Synthesis, Characterization, Theoretical Investigations and Applications)
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Structural Study of Nematogenic Compound 5OS5
by
Aleksandra Deptuch, Bartosz Sęk, Sebastian Lalik, Wojciech Zając, Mirosława D. Ossowska-Chruściel, Janusz Chruściel and Monika Marzec
Crystals 2024, 14(4), 367; https://doi.org/10.3390/cryst14040367 - 13 Apr 2024
Abstract
The S-(4-pentylphenyl) 4-(pentyloxy)benzothioate, forming the nematic phase, is investigated by X-ray diffraction in temperatures between 263 K and 365 K, with the support of differential scanning calorimetry and polarizing optical microscopy. The microscopic observations show changes within the solid state, while X-ray diffraction
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The S-(4-pentylphenyl) 4-(pentyloxy)benzothioate, forming the nematic phase, is investigated by X-ray diffraction in temperatures between 263 K and 365 K, with the support of differential scanning calorimetry and polarizing optical microscopy. The microscopic observations show changes within the solid state, while X-ray diffraction does not indicate any transitions between the crystal phases. The Rietveld refinement shows that the crystal phase formed from the melt is the same monoclinic crystal phase with the P21/c space group as reported for a single crystal grown from an ethanol solution. The temperature dependence of the unit cell parameters in the 263–335 K range is determined and the coefficients of thermal expansion are obtained. The unit cell expands on heating along the longer ac-diagonal and b-axis while, along the shorter ac-diagonal, a very small shrinkage occurs. The diffraction patterns of the liquid crystalline nematic phase indicate the formation of dimers via hydrogen bonding. Density functional theory calculations (def2TZVPP basis set, B3LYP-D3(BJ) correlation-exchange functional) are applied for geometry optimization of an isolated molecule and selected dimers.
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(This article belongs to the Special Issue Liquid Crystal Research and Novel Applications in the 21st Century)
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Open AccessArticle
Indium-Doped SnO2 Based Surface Acoustic Wave Gas Sensor with Ba0.6Sr0.4TiO3 Film
by
Birhanu Alemayehu, Kaushik Annam, Eunsung Shin and Guru Subramanyam
Crystals 2024, 14(4), 366; https://doi.org/10.3390/cryst14040366 - 12 Apr 2024
Abstract
SnO2-based gas sensors have been widely synthesized and used for the detection of various hazardous gases. However, the use of doped SnO2 in sensing applications has recently attracted increased interest due to the formation of a synergistic effect between the
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SnO2-based gas sensors have been widely synthesized and used for the detection of various hazardous gases. However, the use of doped SnO2 in sensing applications has recently attracted increased interest due to the formation of a synergistic effect between the dopant and the host. Moreover, in the case of a surface acoustic wave (SAW) sensor, the piezoelectric material used in the fabrication of the sensor plays a crucial role in defining the response of the SAW sensor. As a ferroelectric material, barium strontium titanate (Ba0.6Sr0.4TiO3) has recently been studied due to its intriguing dielectric and electromechanical properties. Its high acoustic velocity and coupling coefficient make it a promising candidate for the development of acoustic devices; however, its use as a piezoelectric material in SAW sensors is still in its infancy. In this paper, we present the design, fabrication and validation of an indium doped SnO2-based SAW gas sensor on Ba0.6Sr0.4TiO3 thin film for room temperature (RT) applications. Pulsed laser deposition was used to deposit thin films of Ba0.6Sr0.4TiO3 and indium-doped SnO2. Different characterization techniques were employed to analyze the morphology and crystallization of the films. The performance of the fabricated sensor was validated by exposing it to different concentrations of ethanol and then analyzing the recorded frequency shift. The sensor exhibited fast response (39 s) and recovery (50 s) times with a sensitivity of 9.9 MHz/Δ. Moreover, the sensor had good linear response and reproducibility. The fabricated indium-doped SnO2-based SAW gas sensor could be suitable for practical room temperature applications.
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(This article belongs to the Section Inorganic Crystalline Materials)
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Open AccessArticle
High-Temperature Tribological Behavior of Fast-Hot-Pressed NiCr/Cr3C2-LaF3 Self-Lubrication Composite
by
Hao Yang, Chuanbing Huang, Haozhong Lv, Yongjun Liu, Yonghui Sun, Huifeng Zhang, Hao Lan, Yang Wu and Weigang Zhang
Crystals 2024, 14(4), 365; https://doi.org/10.3390/cryst14040365 - 12 Apr 2024
Abstract
This article details a method for preparing cermet matrix composites via Fast hot pressing (FHP) sintering technology and emphasizes their potential use in extremely high-temperature settings. The material primarily consists of NiCr alloy, Cr3C2, and LaF3. An
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This article details a method for preparing cermet matrix composites via Fast hot pressing (FHP) sintering technology and emphasizes their potential use in extremely high-temperature settings. The material primarily consists of NiCr alloy, Cr3C2, and LaF3. An in-depth investigation was conducted on the tribological properties of the specimen by conducting sliding tests against a Si3N4 ball at varying temperatures, including room temperature (RT), 400 °C, 600 °C, and 800 °C. Advanced techniques such as scanning electron microscopy, micro-XRD, and micro-Raman spectroscopy were employed to examine the friction surfaces formed under different frictional temperatures. The findings reveal a uniform composition and high density within the composites. It is noteworthy that as the LaF3 content increases, the hardness of the ceramic phase diminishes. Conversely, the hardness of the alloy phase augments with the addition of LaF3, provided that its content remains below 15 wt%. The composite material containing 15 wt% LaF3 demonstrates superior hardness values, with the ceramic phase reaching HV1412 and the alloy phase achieving HV384. Furthermore, the coefficient of friction of the composite material was evaluated. The coefficient of friction of the composite is between 0.74 and 0.4 and the wear rate is 4.46 × 10−6–5.72 × 10−5 mm3N−1m−1 from room temperature to 800 °C. The lubrication behavior at low temperature is mainly attributed to the lubricating effect of LaF3, and at high temperature it is due to the tribochemical reaction to form LaCrO3 with good lubricating properties, which plays a synergistic lubricating role with Cr2O3.
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(This article belongs to the Special Issue Ceramics: Processes, Microstructures, and Properties)
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Open AccessArticle
Modeling 0.3 THz Coaxial Single-Mode Phase Shifter Designs in Liquid Crystals with Constitutive Loss Quantifications
by
Jinfeng Li and Haorong Li
Crystals 2024, 14(4), 364; https://doi.org/10.3390/cryst14040364 - 11 Apr 2024
Abstract
This work proposes and examines the feasibility of next-generation 0.3 THz phase shifters realized with liquid crystals (LCs) as tunable dielectrics coaxially filled in the transmission line. The classic coaxial transmission line topology is robust to electromagnetic interference and environmental noise, but is
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This work proposes and examines the feasibility of next-generation 0.3 THz phase shifters realized with liquid crystals (LCs) as tunable dielectrics coaxially filled in the transmission line. The classic coaxial transmission line topology is robust to electromagnetic interference and environmental noise, but is susceptible to higher-order modes from microwave to millimeter-wave towards terahertz (THz) wavelength ranges, which impedes the low-insertion-loss phase-shifting functionality. This work thus focuses primarily on the suppression of the risky higher-order modes, particularly the first emerging mode impacting the dielectric loss and metal losses in diverse manners. Based on impedance matching baselines at diverse tuning states of LCs, this work analytically derives and models two design geometries; i.e., design 1 for the coaxial geometry matched at the isotopically referenced state of LC for 50 Ω, and design 2 for geometry matched at the saturated bias of LC with the maximally achievable permittivity. The Figure-of-Merit for design 1 and design 2 reports as 35.15°/dB and 34.73°/dB per unit length, respectively. We also propose a constitutive power analysis method for understanding the loss consumed by constitutive materials. Notably, for the 0.3 THz design, the isotropic LC state results in an LC dielectric loss of 63.5% of the total input power (assuming 100%), which becomes the primary constraint on achieving low-loss THz operations. The substantial difference in the LC dielectric loss between the isotropic LC state and saturated bias state for the 0.3 THz design (35.76% variation) as compared to that of our past 60 GHz design (13.5% variation) indicates that the LC dielectric loss’s escalating role is further enhanced with the rise in frequency, which is more pronounced than the conductor losses. Overall, the results from analytical and finite-element optimization in this work shape the direction and feasibility of the unconventional THz coaxial phase shifting technology with LCs, actioned as continuously tunable dielectrics.
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(This article belongs to the Special Issue Pushing the Boundaries of Liquid Crystal-Enabled Technologies and Applications)
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Open AccessArticle
Nanocrystalline Iron Oxides with Various Average Crystallite Size Investigated Using Magnetic Resonance Method
by
Rafał Pelka, Urszula Nowosielecka, Kamila Klimza, Izabela Moszyńska, Konstantinos Aidinis, Grzegorz Żołnierkiewicz, Aleksander Guskos and Nikos Guskos
Crystals 2024, 14(4), 363; https://doi.org/10.3390/cryst14040363 - 11 Apr 2024
Abstract
A series of nanocrystalline iron oxide samples (M1–M5) which differ from each other in average crystallite size (from 26 to 37 nm) was studied. The raw material was nanocrystalline iron with an average crystallite size equal to 21 nm promoted with hardly reducible
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A series of nanocrystalline iron oxide samples (M1–M5) which differ from each other in average crystallite size (from 26 to 37 nm) was studied. The raw material was nanocrystalline iron with an average crystallite size equal to 21 nm promoted with hardly reducible oxides: Al2O3, CaO, K2O (in total, max. 10 wt%). Nanocrystalline iron was subjected to oxidation with water vapor to achieve different oxidation degrees (α = 0.16–1.00). Metallic iron remaining in the samples after the oxidizing step was removed by etching. Magnetic resonance spectra of all samples were obtained at room temperature. All resonance lines were asymmetric and intense. These spectra were fitted by Lorentzian and Gaussian functions. All spectral parameters depend on the preparation method of the nanoparticles. We suppose that the Lorentz fit gives us a spectrum from larger agglomerated sizes whereas the Gaussian fit comes from much smaller magnetic centers. For the nanocrystalline samples with the largest size of iron oxide nanocrystallites, the highest value of total integrated intensity was obtained, indicating that at smaller sizes, they are more mobile in reorientation processes resulting in more settings of anti-parallel magnetic moments. The magnetic anisotropy should also increase with the increase in size of nanocrystallites.
Full article
(This article belongs to the Special Issue Structure, Thermal and Magnetic Properties of Nanocrystalline Materials)
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