Crystal Research and Technology最新文献

In this communication, the synthesis and characterizations of modified strontium manganate (SrCu_1/3Mn_1/3W_1/3O₃) (SCMWO) by high-temperature solid-state method are reported. The structural analysis predicts a monoclinic structure with a crystallite size of 36.8 nm. The analysis of the Raman active modes reveals the presence of all the constituent atomic vibrations. The study of the ultraviolet–visible spectrum provides a bandgap energy of 1.71 eV, which may be suitable for photovoltaic applications. A Maxwell-Wanger type of polarization effect is observed at low frequency while low dielectric loss makes the material suitable for energy storage devices. The study of the impedance plots reveals the negative temperature coefficient of resistance (NTCR) character. The activation energy increases with both frequency and temperature in the modified perovskite suggesting that conductivity of the sample increases and material characters are changing from dielectric to semiconducting. The symmetrical curves in the electrical modulus plots and shift toward higher frequency region agree with the results of the non-Debye-type of relaxation mechanism. The semicircular curves in the Cole–Cole plots confirm the semiconducting nature and are also well supported by the results of Nyquist plots. The studied material exhibits a semiconductor nature, which may be found suitable for energy storage device applications.

In this study, two morphologies of cerium oxide (CeO₂) abrasive particles, octahedral and spheroidal, are synthesized by solvothermal method using cerium nitrate hexahydrate (Ce(NO₃)₃-6H₂O) as raw material. Fourier infrared spectroscopy, X-ray diffractometer (XRD) and scanning electron microscopy (SEM) are used to characterize the composition and morphology of CeO₂ abrasive particles. The synthesized CeO₂ is used for chemical mechanical polishing (CMP) of the Si surface of 6H-SiC wafers, and the surface morphology of the polished wafers are observed using atomic force microscopy (AFM). After polishing with octahedral and spheroidal abrasive particles, the surface roughness of the wafers are 0.327 and 0.287 nm, and the material removal rates (MRR) are 870 and 742 nm h⁻¹, respectively. Calculations comparing the ultraviolet absorption spectra and bandgap energies of the two types of abrasive particles as well as molecular dynamics (MD) simulations reveal that the synthesized octahedral CeO₂ particles possessed stronger surface chemical activity and material removal performance.

In Cz–Si growth, the shape of the solid–liquid interface and the v/G ratio significantly impact crystal quality. This study utilizes a data-driven approach, employing multilayer perceptron (MLP) neural networks and Bayesian optimization, to investigate the scale-up process of Cz–Si under conditions of partial similarity. The focus is on exploring the influence of various process and furnace geometry parameters, as well as radiation shield material properties, on the critical measures of crystal quality. Axisymmetric CFD modeling produces 340 sets of 18D raw data, from which 14-dimensionless derived data tuples are generated for the design and training of the MLP. The best MLP obtained demonstrates the ability to accurately assess the complex nonlinear dependencies among dimensionless numbers derived from CFD data and, on the output side, interface deflection and v/G. These relationships, crucial for scale-up, are successfully generalized across a wide range of parameters.

In this study, Cadmium Sulfide (CdS) semiconductor films are electrodeposited on Indium Tin Oxide (ITO) substrates at 80 °C base temperature for different boric acid (H₃BO₃) ratios. The effect of boric acid on these films is investigated. For this, first of all, the structural change of the films is examined. Among the films obtained with different boric acid ratios, the optimum film is achieved with 0.06 m boric acid doped. From the basic absorption spectra (αhʋ) of the obtained CdS:B films, the variation of hʋ is drawn and it is determined that the CdS:B semiconductor films has a direct band transition. From the basic absorption spectra of the obtained CdS:B films, it is observed that the CdS:B semiconductor films has a direct band transition. In addition, the optical energy bandgap values obtained are in agreement with the values in the available literatures. The results of the structural, optical, and morphological properties of the films produced in this study indicate that among the selected additive ratios, 1% boric acid gives the best and optimum deposition condition. The thin films obtained are also found to be useful as absorber layers in photovoltaic solar cells.

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.

Mist chemical vapor deposition (mist-CVD) is expected to be a potentially low-environment-impact and low-cost crystal growth technique. With mist-CVD, soluble materials are usually selected as raw materials, and mist is usually generated from an aqueous solution including raw materials. However, any substances to be included in the mist can be potentially supplied as raw materials. Namely, there is no need for the substances to be dissolved in some solvent. Therefore, as a trial, it is demonstrated that mist including poorly soluble particles are used as raw materials for mist-CVD crystal growth.

Employing density functional theory within the Wien2k code, first-principle calculations are conducted to explore the impact of applied pressure up to 80 GPa on the structural, mechanical, thermal, and electronic characteristics of BaPbO₃. Demonstrating metallic behavior with ductile attributes, BaPbO₃ exhibits a decreasing anisotropic nature under escalating pressure. Evaluation of cubic elastic constants, optimization curves, and enthalpy of formation indicates the compound's mechanical and thermodynamic stability under high pressure conditions. Calculated values of C₁₁ and C₄₄ reflect heightened resistance to unidirectional compression and increased stiffness under pressure. These mechanical properties position BaPbO₃ as a promising candidate for diverse industrial applications across varying pressure ranges, including utilization in piezoelectric materials (0–20 GPa) and high-pressure sensors. Additionally, charge density contours suggest a combination of ionic (Ba─Pb) and covalent bonding (Pb─O) within the compound's constituent atoms. The material can exhibit potential applications as a piezoelectric sensor at 0–20 GPa, high-pressure actuators ≈20 GPa, and as a high melting temperature resistive substrate for laser welding and cutting materials.

Calcium pyroniobate (Ca₂Nb₂O₇) as a kind of lead-free piezoelectric material has been applied for different fields, but the study of isothermal and non-isothermal growth behaviors of Ca₂Nb₂O₇ in the molten slag is infrequent. In this paper, the in situ thermal analyzer with a single hot thermocouple technique (SHTT) is used to study the growth behaviors of Ca₂Nb₂O₇ in molten slag. In the isothermal temperatures, the Ca₂Nb₂O₇ presents two kinds of growth morphology, including three dimensional (3D) rhombus growth and fibrous one dimensional (1D) growth. The 3D rhombus is grown under the range of 1608 to 1628 K. When the temperature further decreases to 1593 K, the growth behavior of Ca₂Nb₂O₇ becomes fibrous in 1D. Growth velocity affected by the degree of supercooling may account for the phenomenon of two kinds of growth behaviors in different temperatures. In the non-isothermal growth process, the cooling rate over 10 K min⁻¹ contributes to multiple crystal nucleuses growth of Ca₂Nb₂O₇. The cooling rate below 5 K min⁻¹ leads to single nuclear growth. This paper provides a control guideline for Ca₂Nb₂O₇ growth.

This study investigates the structural, mechanical, electronic, magnetic, and thermoelectric properties of ZrMnX (X = As, Sb, Te) half Heusler alloys using spin-polarized density functional theory (SPDFT) with WIEN2K code using full potential linearized augmented plane wave(FP- LAPW) technique. Results indicate the ferromagnetic phase’s stability over the non-magnetic phase in all three alloys. Band structures and density of states highlight the half-metallic nature of ZrMnX. These alloys exhibit mechanical stability, ductility, and directional properties. Magnetic moments align with the Slater–Pauling rule. Thermoelectric properties, including Seebeck coefficient, electrical and thermal conductivity, and thermoelectric figure of merit, are evaluated using semi-classical Boltzmann theory. The Seebeck coefficient values for ZrMnX (X = As, Sb, Te) are 144.7, 123.3, and −182.6 µV K⁻¹, respectively at 1200 K with corresponding highest figure of merit 1.0, 0.7, and 1.78. These findings suggest the suitability of these alloys for spintronic devices and high-temperature thermoelectric applications due to their observed spin-polarized character and high figure of merit.