Lattice Parameters Research Articles

Er3+ doped BZBO single crystal: Growth and electro-elastic property characterization

Large-sized and high-quality Er: Bi2ZnB2O7 (Er: BZBO) single crystal has been grown using the Kyropoulos method. The crystal structure is refined by the Rietveld method, Er: BZBO belongs to the orthorhombic system and space group Pba2, lattice parameters: a = 10.811(1) Å, b = 11.006(1) Å, c = 4.8817(4) Å, which are slightly reduced after doping with Er3+. The thermal expansion anisotropy is studied and shows a decrease with coefficients of α11 = 7.69(1) × 10−6 K−1, α22 = 9.90(9) × 10−6 K−1, and α33 = 1.98(8) × 10−6 K−1, respectively. The relative dielectric constants are found to be εT11/ε0 = 32.8(1), εT22/ε0 = 17.2(1), and εT33/ε0 = 17.0(9), respectively. The dielectric, elastic, and piezoelectric constants for the Er: BZBO crystal are determined by the impedance method, with the piezoelectric coefficients d15, d24, d31, d32 and d33 are measured as 1.1(9), −5.4(2), 1.8(7), −5.9(1) and 1.1(5) pC/N, respectively. Furthermore, the temperature dependence of the piezoelectric coefficients from room temperature to 500 °C is evaluated, showing good temperature stability for d24 and d32 with variations were −7 % and 13 %, respectively.

3D electron diffraction studies of synthetic rhabdophane (DyPO4·nH2O).

In this study, we report the results of continuous rotation electron diffraction studies of single DyPO4·nH2O (rhabdophane) nanocrystals. The diffraction patterns can be fit to a trigonal lattice (P3121) with lattice parameters a= 7.019 (5) and c= 6.417 (5) Å. However, there is also a set of diffuse background scattering features present that are associated with a disordered superstructure that is double these lattice parameters and fits with an arrangement of water molecules present in the structure pore. Pair distribution function (PDF) maps based on the diffuse background allowed the extent of the water correlation to be estimated, with 2-3 nm correlation along the c axis and ∼5 nm along the a/b axis.

The potential of Gd doping as a promising approach for enhancing the adsorption properties of nickel-cobalt ferrites.

The study shows that the addition of gadolinium ions has a significant impact on the structure, morphology, and adsorption properties of Ni-Co spinel ferrite that was synthesized by the sol-gel auto-combustion method. The research also indicates that the higher the Gd content, the greater the increase in the lattice parameter, which suggests that Gd3+ ions uniformly replaced the octahedral Fe3+ ions. The morphology and chemical composition of Gd-doped Ni-Co ferrites have been studied using SEM and EDS. Gd adding to the NiCoFe matrix increases the BET surface area by 50% (from 48 to 72 m2/g) and promotes the formation of mesopores with an average radius from 3.9 to 4.9nm. The pHPZC values of Gd-doped ferrites are in the range of 7.22-7.39, which means that the ferrite surface will acquire a positive charge at natural pH, so this will promote the adsorption of Congo red anionic dye through electrostatic interaction forces. Langmuir, Freundlich, and Dubinin-Radushkevich models were used to explain the mechanism of CR adsorption on the Ni0.5Co0.5GdxFe2-xO4 adsorbent surface. The ionic-covalent parameter has been estimated to describe the surface acid-base properties. Overall, this study highlights the potential of Gd3+ doping as a promising approach for enhancing the adsorption properties of nickel-cobalt ferrites.

The Effect of In Concentration and Temperature on Dissolution and Precipitation in Sn-Bi Alloys.

Sn-Bi-based, low-temperature solder alloys are being developed to offer the electronics manufacturing industry a path to lower temperature processes. A critical challenge is the significant microstructural and lattice parameter changes that these alloys undergo at typical service temperatures, largely due to the variable solubility of Bi during the Sn phase. The influence of alloying additions in improving the performance of these alloys is the subject of much research. This study aims to enhance the understanding of how alloying with In influences these properties, which are crucial for improving the alloy's reliability. Using in situ heating synchrotron powder X-ray diffraction (PXRD), we investigated the Sn-57 wt% Bi-xIn (x = 0, 0.2, 0.5, 1, 3 wt%) alloys during heating and cooling. Our findings reveal that In modifies the microstructure, promoting more homogeneous Bi distribution during thermal cycling. This study not only provides new insights into the dissolution and precipitation behaviour of Bi in Sn-Bi-based alloys, but also demonstrates the potential of In to improve the thermal stability of these alloys. These innovations contribute significantly to advancing the performance and reliability of Sn-Bi-based, low-temperature solder alloys.

Ab-Initio calculations on physical properties of Dirac semimetal AMgBi (A=K, Rb, Cs)

This study presents a comprehensive first-principles investigation of the structural, mechanical, vibrational, thermodynamic and electronic properties of AMgBi (A = K, Rb, Cs) compounds using Density Functional Theory. Also, the effect of substituting alkali atoms on the physical properties has been discussed. The tetragonal PbClF-type structure has been confirmed by the analysis and the results revealed good agreement between calculated and experimental lattice parameters for KMgBi. The mechanical properties have been investigated for the first time for RbMgBi and CsMgBi. The mechanical stability of the materials in the ground state has been confirmed through the use of obtained elastic constants. Furthermore, derived parameters from elastic constants such as bulk modulus, shear modulus, and Poisson's ratio indicated that the materials are brittle and exhibited anisotropic mechanical behavior due to their layered structure. This study conducts a detailed analysis of phonon modes, explores their connections to thermal and elastic properties, visualizes the movements of phonon modes at the gamma point, determines Born effective charges, and discusses LO/TO splitting, which is for the first time for RbMgBi and CsMgBi. Phonon dispersion calculations confirmed the dynamical stability of the compounds and revealed the presence of phonon band gaps, supporting their quasi-two-dimensional nature. Investigation of thermodynamic properties using the quasi-harmonic approximation has shown the temperature dependence of internal energy, Helmholtz free energy, specific heat, and entropy for the first time for all compounds. The materials exhibited relatively low thermal conductivity, following the order KMgBi > RbMgBi > CsMgBi. The calculated Grüneisen parameter values were found to be 1.42, 1.44, and 1.53 for KMgBi, RbMgBi, and CsMgBi, respectively, suggesting relatively weak anharmonicity within the materials.

Effects of applied pressure on structural, electronic, and optical properties of magnesium incorporated wurtzite beryllium oxide at different magnesium compositions

The effects of applied pressure on the structural, electronic, and optical properties of magnesium-incorporated wurtzite beryllium oxide (w-BeO) at different magnesium compositions are calculated. Each compound at different applied pressures confirms stability in the wurtzite phase. At different applied pressures, the equilibrium lattice constants (a0, c0) increase, but the bulk modulus (B0) and the c0/a0 ratio decrease with increasing magnesium composition. With increasing pressure, the lattice constants of each specimen decrease nonlinearly. Each compound possesses a wide direct band gap (Г-Г) at different applied pressures. The calculated band gap decreases with increasing magnesium composition at different applied pressures. With an increase in applied pressure, the band gap of each compound increases. Each wurtzite specimen is optically anisotropic and exhibits birefringence. Electronic excitations from O-2p to Be-2s, 3p and Mg-3s, 3p are responsible for the various optical features of the considered alloys. At different applied pressures, static optical constants ε1(0), n(0), and R(0) increase, but critical points in the ε2(ω), k(ω, σ(ω), and α(ω) spectra decrease with increasing magnesium composition. For each specimen, components of static optical constants reduce, while components of critical point energies increase with an increase in applied pressure.

DFT-based simulation for the semiconductor behavior of XGeCl3 (X=K, Rb) halide perovskites under hydrostatic pressure

In this work, the structural and electronic properties of XGeCl3 (X=K, Rb) crystallized in cubic cell (Pm-3m, 221) were presented under hydrostatic pressure from 0 to 8 GPa using the first-principal Density Functional Theory (DFT) under the Perdew–Burke–Ernzerhof (PBE) form of the generalized gradient approximation (GGA). The Projector Augmented Wave (PAW) method describing electron–ion interaction was used here. For XGeCl3 (X=K, Rb), the lattice constants were calculated as 5.171 and 5.197 Å, and the band gaps were predicted as 0.5802 and 0.657 eV, respectively at ambient pressure. It was observed that the lattice parameters and bond lengths of the XGeCl3 (X=K, Rb) compounds decreased with increased pressure. The applied hydrostatic pressure reduced the band gaps, and the metallic character was detected at 5 GPa for both structures. This study provides a theoretical basis that may have potential uses in optoelectronic applications of the XGeCl3 (X=K, Rb) perovskites.

High Milling Time Influence on the Phase Stability and Electrical Properties of Fe50Mn35Sn15 Heusler Alloy Obtained by Mechanical Alloying.

Fe50Mn35Sn15 Heusler alloy, obtained by mechanical alloying, was subjected to larger milling times in the range of 30-50 h to study the phase stability and morphology. X-ray diffraction studies have shown that the milled samples crystallise in a disordered A2 structure. The A2 structure was found to be stable in the milling range studied, contrary to the computation studies performed on this composition. Using Rietveld refinements, the lattice parameter, mean crystallite size, and lattice strain were computed. The nature of the obtained phases by milling was found to be nanocrystalline with values below 50 nm. A linear increase rate of 0.00713 (h-1) was computed for lattice strain as the milling time increased. As the milling time increases, the lattice parameter of the cubic Heusler was found to have a decreasing behaviour, reaching 2.9517 Å at 50 h of milling. The morphological and elemental distribution-characterised by scanning electron microscopy and energy-dispersive X-ray spectroscopy-evidenced Mn and Sn phase clustering. As the milling time increased, the morphology of the sample was found to change. The Mn and Sn cluster size was quantified by elemental line profile. Electrical resistivity evolution with milling time was analysed, showing a peak for 40 h of milling time.

First principles theoretical of designing Sandwich-like Metallic BP4 Monolayer as Anode for Alkali Metal-ion Batteries.

Phosphorene has been widely used as anode material for batteries. However, the huge volume change during charging and discharging process, the semiconductor properties, and the high open circuit voltage limit its application. Based on this, by introducing the electron-deficient boron atoms into blue phosphorene, we proposed a P-rich sandwich-like BP4 monolayer by density functional theory calculation and particle swarm optimization. The BP4 monolayer shows good thermodynamic and dynamic stability, as well as chemical stability in O2 atmosphere, mainly due to the strengthened P-P bond of the outer layer by the middle boron atoms adopting sp3 hybridization. According to the band structure, the BP4 monolayer shows metallic property, which is beneficial to electron conductivity. Furthermore, compared with blue phosphorene and black phosphorene, the P-rich BP4 monolayer shows higher theoretical capacity for Li, Na, and K of 1193.90, 1119.28, and 397.97 mA·h·g-1, respectively. The lattice constant of BP4 monolayer increases only 3.73 (Li), 2.52 (Na) after Li/Na fully adsorbed on the anode. More importantly, the wettability of BP4 monolayer in the electrolyte is comparable to that of graphene. These findings show that the stable sandwich-like BP4 monolayer has potential as a lightweight anode material.

Synthesis, Studies of HDTDHP-μ Crystals from Arundina graminifolia Specimen for Electronic, Photonic, Optical and Electrical Use Correlated with Macro-Crystals for Sensor and Display Uses

A 7-hydroxy-2,4-dimethoxy-9,10-dihydrophenanthrene-HDTDHP macro-crystalline sample is synthesized in a time duration of 23 days with a monoclinic form of crystal with space group as P21/n and the lattice constants are slightly higher than earlier reported macro-HDTDHP. The macro ones are well-milled to get the micro ones and a scanning electron microscopy study of the HDTDHP-μ crystal was analyzed to identify the micro level average scaling in microns. The increased value of the dielectric constant at lower range of frequencies is by the effect of all kinds of polarizations; also, the dielectric loss is measured as decrease in values with the increase in frequencies at room temperature. The electronic-micro filter use is 4.0196 microns for micro influx as the proper opto-electronic, extended NLO type employability as ascertained from transmittance spectral data. The HDTDHP micro-crystalline material is mainly used in micro-photonics, in filtering as micro-influx delineation, in NLO usefulness as opto-electronic agent by the transmittance data and in frequency enhancing and projective utilization in displays. Also, display profile of (111) mode of HDTDHP by without and with recursively assigned colors for RGBR polygonal matrix by software and sensor work sensitiveness of both scaling are measured and reported.

Structural and Magnetic Properties of Nano Manganite La0.6Sr0.4MnO3 Obtained by Mechanochemical Synthesis Influenced by Preparation Conditions

Single phase La0.6Sr0.4MnO3 nanoparticles with perovskite structure ( R3̅C symmetry) were successfully prepared by ball milling (mechanochemical synthesis) for 1 and 10 h followed by annealing treatment at temperature 900 or 1100 °C. It was found that, the lattice parameters increase with the increase of milling time or annealing temperature. The increase of the annealing temperature results in the increase of crystallite size and the particle size. The obtained samples were found to be ferromagnetic at room temperature. The sample obtained by one hour of milling and 900 °C annealing showed high value of saturation magnetization (about 56 emu g−1) and small value of coercivity (about 31 Oe) at room temperature, while the other samples show reduced value of magnetization and higher value of coercivity. The obtained magnetic results are discussed in light of the core/shell model of nanoparticles. The effect of the presence of oxygen vacancies on the lattice parameters and magnetic properties of the obtained samples is also discussed.

Obtaining parallax-free X-ray powder diffraction computed tomography data with a self-supervised neural network

In this study, we introduce a method designed to eliminate parallax artefacts present in X-ray powder diffraction computed tomography data acquired from large samples. These parallax artefacts manifest as artificial peak shifting, broadening and splitting, leading to inaccurate physicochemical information, such as lattice parameters and crystallite sizes. Our approach integrates a 3D artificial neural network architecture with a forward projector that accounts for the experimental geometry and sample thickness. It is a self-supervised tomographic volume reconstruction approach designed to be chemistry-agnostic, eliminating the need for prior knowledge of the sample’s chemical composition. We showcase the efficacy of this method through its application on both simulated and experimental X-ray powder diffraction tomography data, acquired from a phantom sample and an NMC532 cylindrical lithium-ion battery.

Rapid Synthesis and Sintering of La2O2S and Its Physical, Optical, and Mechanical Properties

Rare-earth oxysulfides are a class of functional ceramic materials with excellent physico-chemical properties and rich functionality. In this study, La2O2S powders were prepared from La2S3 and La2O3 powders at 1000 °C by pressureless sintering. La2O2S compacts were synthesized from La2S3 and La2O3 powders at 800–1600 °C by spark plasma sintering. The influences of sintering temperature and time on the preparation of La2O2S were studied. XRD results indicated that La2O2S ceramics were synthesized successfully and that the lattice constants of La2O2S were close to the theoretical values. SEM showed that the microstructure of La2O2S compacts was homogeneous. The specific heat of La2O2S mainly came from lattice contribution, and its Debye temperature was 237 K. The UV–visible absorption spectra showed different absorption levels in the 240–300 nm range. Raman spectroscopy revealed distinct peaks at different temperatures, indicating changes in the covalence band. The relative density of La2O2S ceramics was 92% and lower than theoretical values. Hardness of the synthesized La2O2S was greater than that of Gd2O2S ceramics.

Structural distortion-induced low-temperature dielectric dispersion in lanthanide titanate pyrochlores

Rare-earth titanate pyrochlores have attracted significant attention for their unique magnetic frustration; however, research on the origin of low-temperature dielectric dispersion and the relationship between dielectric properties and structure lags far behind. Here, by systematically investigating the dielectric properties of representative rare-earth titanates R2Ti2O7 (R = La, Nd, Sm, Er, Yb, and Lu), we demonstrate that R2Ti2O7 with a cubic pyrochlore structure exhibits low-temperature dielectric dispersion behavior, while the other compounds with a monoclinic perovskite-like layered structure possess no dispersion behavior but excellent temperature-stable dielectric property. The dielectric dispersion in cubic pyrochlores arises from the structural distortion. Furthermore, the existence of structural distortion is affirmed by the anomalous phonon softening of A1g Raman mode around the dielectric dispersion temperature, and the origin of the structural distortion is attributed to anharmonic phonon–phonon interactions induced by intrinsic vacant oxygen at Wyckoff 8a sites. In addition, with increasing ionic radius from R = Lu to Sm, the increased lattice parameter leads to varied bond length and bond angle of Ti-O(1)-Ti, which strengthens the local lattice distortion of TiO(1)6 octahedra and thus enhances diffusion degree of dielectric dispersion. On the other hand, the absence of intrinsic vacant oxygen site hardly gives rise to the local structural distortion and thus no dielectric dispersion in monoclinic R2Ti2O7. Our work not only clarifies the mechanism of dielectric dispersion but also gives a comprehensive perspective on the structure–property relationship of rare-earth titanates R2Ti2O7, and thus lays a solid foundation for further work on related materials.

Formation of pseudo-morphic domain in Cr2O3(0001) epitaxial film grown on α-Al2O3(0001) and its effect on Néel temperature

To address the issue of the impact of the epitaxial strain on the Néel temperature T N, we investigated the formation of the epitaxial domain in the Cr2O3 layer grown on the α-Al2O3(0001) substrate isostructural to Cr2O3 and determined T N of the fabricated films. We varied the sputtering power for the Cr2O3 growth from 10 W to 40 W to alter the strain condition of the epitaxial film. When the sputtering power is 10 W, the single epitaxial domain is formed, whereas the pseudo-morphic and relaxed domains coexist for the sputtering power above 20 W. T N decreased from about 271 K to below 252 K accompanied by the formation of the two types of epitaxial domains. The lattice parameters of the pseudo-morphic domain are beyond the elastic deformation approximation adopted in the theoretical approaches, suggesting that the correlation between the T N value and the microstructure also goes beyond the existing theoretical framework.

Crystal structure, chemical bonds and microwave dielectric properties of ultra-low loss Li2Mg2GaTi2O8F ceramics

Ceramics of Li2Mg2GaTi2O8F (LMGTOF) were prepared by the traditional solid-state method. XRD and TEM results confirmed that a single phase of Li2Mg2GaTi2O8F, with an Fd-3m space group and a cubic spinel structure, was formed by the ceramics. It was shown by the results that the lattice parameters of the ceramics at 1050 °C were measured as a = b = c = 8.36576 Å, with a volume of V = 585.485549 Å3. Furthermore, it was observed through the analysis of the Raman peak at 718 cm−1 that an inverse relationship was exhibited between the Raman shift and εr. Similarly, an opposing trend was also demonstrated between the Q × f value and FWHM. By bond valence analysis, it was shown that Mg2+, Ga3+, and Ti4+ ions were in a “rattling” state, and the large positive deviation between εcorr and εtheo was attributed to the strong “rattling” effect induced by the cations. At 1050 °C, the best microwave dielectric properties (εr = 14.58, Q × f = 76,689 GHz, and τf = −52 ppm/°C) were exhibited by LMGTOF ceramics.

Thermoelectric Performance of Non-Stoichiometric Permingeatite Cu3+mSbSe4.

Non-stoichiometric permingeatites Cu3+mSbSe4 (-0.04 ≤ m ≤ -0.02) were synthesized, and their thermoelectric properties were examined depending on the Cu deficiency. Phase analysis by X-ray diffraction revealed no detection of secondary phases. Due to Cu deficiency, the lattice parameters of tetragonal permingeatite decreased compared to the stoichiometric permingeatite, resulting in a = 0.5654-0.5654 nm and c = 1.1253-1.1254 nm, with a decrease in the c/a ratio in the range of 1.9901-1.9903. Electrical conductivity exhibited typical semiconductor behavior of increasing conductivity with temperature, and above 423 K, the electrical conductivity of all samples exceeded that of stoichiometric permingeatite; Cu2.96SbSe4 exhibited a maximum of 9.8 × 103 Sm-1 at 623 K. The Seebeck coefficient decreased due to Cu deficiency, showing p-type semiconductor behavior similar to stoichiometric permingeatite, with majority carriers being holes. Thermal conductivity showed negative temperature dependence, and both electronic and lattice thermal conductivities increased due to Cu deficiency. Despite the decrease in the Seebeck coefficient due to Cu deficiency, the electrical conductivity increased, resulting in an increase in the power factor (especially a great increase at high temperatures), with Cu2.97SbSe4 exhibiting the highest value of 0.72 mWm-1K-2 at 573 K. As the carrier concentration increased due to Cu deficiency, the thermal conductivity increased, but the increase in power factor was significant, with Cu2.98SbSe4 recording a maximum dimensionless figure-of-merit of 0.50 at 523 K. This value was approximately 28% higher than that (0.39) of stoichiometric Cu3SbSe4.

Crystal structure evolution and solid solution mechanism of Al2O3-Cr2O3 system under different reaction conditions

The (Al1-xCrx)2O3 solid solution (ACS) is expected to be an low pollution chromium source for high-performance alumina-chromium oxide refractory materials. In this work, the effects of Cr2O3 content and reaction conditions on the solid solution behavior in the Al2O3-Cr2O3 system were explored and the mechanism was revealed. The relationship between the lattice parameters of the formed ACS phase and the content of Cr2O3 was closer to a linear one as the temperature rose, serving as an indicator for a higher degree of reaction. The solid solution reaction between Al2O3 and Cr2O3 was governed by the diffusion processes of Al3+ and Cr3+ at 1300–1500 °C and 1200 °C, respectively, and thus the increase of Cr2O3 content slowed the solid solution reaction at a low temperature whereas promoted it at elevated temperatures. The diffusion process of solid solution reaction within the Al2O3-Cr2O3 system was consistent with the Cater model; The diffusion activation energy (Ea) decreased as the content of Cr2O3 increased at 1300–1500 °C. When the content of Cr2O3 increased from 25 to 60 mol%, the diffusion activation energy decreased from 92.48 to 86.49 kJ/mol−1, which was attributed to the augmentation in the diffusion rate of Cr3+ caused by the increase of Cr2O3 content and its vapor-phase transport mechanism at high temperatures.

Optical transmittance range of High-Temperature stable phase germanium dichalcogenide (GeS2) single crystal grown by the Bridgman method

A high-temperature (HT) stable phase germanium dichalcogenide (GeS2) was grown in an evacuated quartz ampoule to investigate its transparency range. First, as a starting material for the crystal growth of HT-GeS2, GeS2 glass containing HT-GeS2 crystals was synthesized using our previously improved process for synthesizing polycrystalline sulfide compounds in a conventional horizontal furnace. The HT-GeS2 crystal was grown using the Bridgman method under a temperature gradient of 20–30 °C/cm. The grown HT-GeS2 single crystal was easily cleaved along the growth direction, and this cleaved surface was identified as the (001) face using X-ray diffraction (XRD). Single-crystal XRD analysis confirmed the growth of an HT-GeS2 single crystal with a monoclinic structure (space group P21/c) and lattice parameters of a = 6.7061(4) Å, b = 16.0877(13) Å, and c = 11.4242(11) Å, and β = 91.069 (8)°. The optical transmittance spectra of the HT-GeS2 single crystal were measured in the visible and infrared (IR) regions, revealing a transparency range of 0.36–22.5 μm. Differential thermal analysis revealed the melting point of HT-GeS2 as 841 ± 1 °C. The HT-GeS2 single crystal is expected to be a new candidate for IR optical crystal.

Customization of indium-based MOFs for enhanced adsorptive and photocatalytic of organic pollutants: Morphology involvement on performance and mechanism

Metal-organic frameworks (MOFs) as photocatalysts are promising candidates for environmental wastewater treatment owing to their tunable crystal structure, well-ordered donor–acceptor interface, and exceptional porosity. However, precise control over size and morphologies of MOFs to enhance adsorptive and photocatalytic performance is still a considerable challenge. Herein, the MIL-68(In)–NH2 (MN) MOFs with special acicular structure are customized by a facile method, in which the growth of crystal nuclei is inhibited and regulated by pyridine. The formation mechanism of MN with different morphologies and size is introduced, and their photocatalytic activities are systematically explored by degrading model pollutants tetracycline (TC) and dyes under visible light irradiation. Benefiting from its high specific surface area and the exposed large lattice spacing facet, the wool-ball morphology MN (MN-W) with surface acicular nanostructure presents an optimum photocatalytic performance compared to other MN morphologies. The MN-W also exhibits excellent adsorption capacity, remarkable cyclic stability, and good practical organic wastewater treatment capability. The possible photodegradation mechanism and pathways are elucidated, demonstrating that h+ is the primary reactive species, followed by •OH and •O2– radicals, responsible for the degradation of TC. This work is anticipated to tailoring design and modulate MOF photocatalysts for boosting the photocatalytic performance towards organic effluents remediation.