Crystal Research and Technology最新文献

In this study, the propagation of plane waves in the lanthanum gallium tantalate (langatate, LGT) single crystals is investigated. Moreover, the flight time of different waves in the LGT rectangular parallelepiped sample is measured using the ultrasonic pulse-echo (UPE) technique, and the elastic constants of the LGT sample are determined. The experimental results clearly show echoes corresponding to the longitudinal and transverse waves along the x-axis. The waves along the z-axis have a similar property. However, the waves along the y-axis are more complex than those along the x- and z-axes. The echoes corresponding to the quasi-longitudinal waves along the y-axis are clear, but those corresponding to the transverse and quasi-transverse waves along the y-axis are not. The elastic constant can be accurately determined if the wave echoes corresponding to this constant propagate without distinct distortion and are clear; otherwise, it may be impossible to accurately determine the constant using UPE. All elastic constants $�c_{�i�j�}^E$ except $�c_{13}^E$ of the LGT single crystals can be determined using UPE from one sample. This study uses UPE to provide a reference for the characterization of elastic constants of piezoelectric crystals with 32 symmetry from one sample.

In this paper, it is found that taking a semitransparent melt, influences c–m interface shape, heat transfer, melt flow and von Mises thermal stress distributions, therefore the quality of the grown crystal. As a result, when absorption coefficients of both melt and crystal change from transparent to opaque case, the c–m interface convexity reduces from 12.5 to 5.8 mm, its shape becomes more convex toward the melt, and the maximum von Mises thermal stresses decreases from 69.55 to 13.8 MPa. For the second study, where the crystal absorption coefficient is fixed at $��20��m^{�-�1�}�$, the c–m interface convexity increases with the increase in melt absorption coefficient. The maximum and minimum von Mises stresses for the case $��100��m^{�-�1�}�$ are low compared to other values; then the grown crystal has a good quality.

A series of copper hydroxyphosphate (Cu₂(OH)PO₄) microcrystals with different shapes, including straw sheaf-like microcrystals, microrods-assembled microflowers, four-edged arrow-like microcrystals, and four-pointed star-like dendrites, are prepared by a hydrothermal method in Na₂HPO₄-NaOH buffer solutions. The buffer solutions serve as both reactant and solvent. More importantly, the pH values of the alkaline buffer solutions significantly affect the morphologies of Cu₂(OH)PO₄ microcrystals. Four samples have absorption bands in the near-ultraviolet, visible, and near-infrared regions; furthermore, four Cu₂(OH)PO₄ microcrystals exhibit different band gap energies (3.06, 2.78, 2.68, and 2.39 eV) owing to their different structures. This strategy can be scaled up for the simple, green, and low-cost production of Cu₂(OH)PO₄ microcrystals.

A twin-crystal magnesium (Mg) model with 9 different symmetric tilt grain boundary (STGB) angles (20°–80°) with preset nanohole defects is established by atomsk and lammps software. The mechanical behavior of grain boundary (GB) angles on twin-crystal Mg with cavity defects and its cavity evolution are simulated by the molecular dynamics method with embedded atomic potential, and the plastic deformation mechanism is revealed. The results show that the yield stress decreases with the increase of the STGB Angle during the stretching process. When the GB Angle increases from 20° to 80°, the yield stress decreases from 2.28 to 1.42 Gpa. This is because the larger the STGB Angle is, the larger the Schmidt factor is, and the easier it is to start dislocation slip during the stretching process. On the other hand, the larger the Angle of STGB, the more the number of atomic voids at the interface, and the more the number of dislocation nucleation points. The larger the Angle of STGB, the lower the strength of twinning Mg but the better the plasticity to avoid fracture. The plastic deformation mechanism mainly includes the nucleation of Shockley incomplete dislocation at STGBs, dislocation slip generates stacking faults (SFs), GB migration, and base plane dislocations.

The beneficiation of low-grade phosphate ore leads to the production of a substantial quantity of phosphate tailings, thereby not only occupying land but also endangering the environment and potentially posing safety concerns. In this work, extrusion molding, steam-curing, and calcined phosphate tailings are employed to fabricate lightweight wall materials with superior strength. It is found that the wall material has a special structure of interwoven needle-like crystals as a way to provide high flexural strength. The main composition of 34.94% phosphate tailings, 36.75% calcined phosphate tailings, 16.64% silica fume, 6.67% anhydrous magnesium sulfate is required to achieve an optimal maintenance process for 4 h of heat preservation at 120 °C saturated vapor pressure environment. The prepared wall materials yield a flexural strength of 24.9 MPa, compressive strength of 18.9 MPa, softening coefficient of 0.81, apparent density of 1.594 g cm⁻³, and thermal conductivity of 0.269 w/(m K), which meet the requirements of the Chinese standard “Lightweight strip board for building partition walls”. Moreover, the calculation revealed that phosphate tailings have a comprehensive utilization rate of 77.23%, effectively mitigating the issues arising from their accumulation and serving as an efficient means of utilizing solid waste derived from phosphate tailings.

The interfacial bonding state between each oxide and the silver matrix in AgCuOIn₂O₃SnO₂ electrical contact materials remains unclear. To address this, first-principles calculations using density-functional theory are employed to establish the low-index surfaces of Ag and SnO₂ and perform convergence tests. Computational results reveal that the Ag (111) surface and the SnO₂(110)-O surface exhibit the highest stability among their respective low-index surfaces. Consequently, these surfaces are chosen to form the interfacial model, and their atomic structure, adhesion work, and interfacial energies are systematically analyzed. The results demonstrate that the stability and interfacial bonding strength of the Ag(111)/SnO₂(110)-O interface are high, exhibiting metallic properties and strong conductivity. Moreover, at an interface spacing of d₀ = 2.4 Å, the interface stability is optimal. The redistribution of charge at the interface induces significant changes in the local atomic density of states, particularly noticeable in the Ag and O atoms. Additionally, the Ag/SnO₂ interface is predominantly bonded through ionic interactions, contributing to its robust bonding.

In this study, semitransparent lead films serve as substrates for depositing niobium pentoxide thin films, forming versatile electro-optical devices. Using vacuum evaporation and ion sputtering techniques at ≈10⁻⁵ mbar, stacked layers of crystalline Pb and amorphous Nb₂O₅ are created. This process reduces free carrier absorption in Nb₂O₅ and forms Urbach tail states with a width of 0.91 eV. Pb/Nb₂O₅ thin films exhibit remarkable broadband absorption, exceeding 440% in the visible and 98% in the infrared. Moreover, Pb substrates induce a redshift in Nb₂O₅’s energy bandgap. Electrical analysis using impedance spectroscopy on Pb/Nb₂O₅/Ag structures reveals their series/parallel resonance and bandstop filter properties. Notably, the bandstop filters exhibit reflection coefficient minima at a notch frequency of 1.66 GHz, with a bandwidth of 280 MHz, return loss of 26 dB, and voltage standing wave ratio of 1.13. These findings underscore the device's potential for wide-ranging electro-optical applications across the electromagnetic spectrum.

Cover image provided courtesy of Jianguang Zhou, Research Center for Analytical Instrumentation, Institute of Cyber-Systems and Control, State Key Laboratory of Industrial Control Technology, Zhejiang University, China.

In order to explore the crystallization behavior of Co-doped amorphous manganese dioxide(Co-doped AMO) and to investigate the electrochemical properties of its different crystallization products as cathodes for aqueous zinc ion batteries. In this work, the effects of heat treatment temperature on the microstructure and phase composition of Co-doped AMO and their electrochemical properties of Zn-MnO₂ battery cathode materials are systematically investigated. The results show that Co-doping increases the crystallization temperature of pure AMO. When the heat treatment temperature is 400 °C, Co-doped AMO is amorphous. At 500 and 550 °C, part of the Co-doped AMO crystallizes into tetragonal spinel structured (Co, Mn)(Co, Mn)₂O₄ material between MnCo₂O₄ and Mn₃O₄. At 650 °C, the crystallized product is completely nano-α-Mn(Co)O₂ crystal. The maximum discharge specific capacities and the retention rate after 100 cycles of the samples at 100 mA g⁻¹ are 325.40 mAh g⁻¹, 86.88%; 217.00 mAh g⁻¹, 13.94%; 186.68 mAh g⁻¹, 41.01%; and 149.03 mAh g⁻¹, 31.27% for the unheated and 400, 550, 650 °C heat-treated samples, respectively. It is proved that the Co-doped AMO without heat treatment is superior to the partially or fully crystallized materials in terms of comprehensive performance and cost as cathode materials for AZIB.