Crystal Research and Technology最新文献

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.

This study investigates the influences of the evaporation temperature and Mg²⁺ concentration on the crystallization of an ammonium sulfate mother liquor. Specifically, their effects on the solubility, metastable zone width, crystallization amount, average particle size, and coefficient of variation of ammonium sulfate are examined through the laser and evaporation crystallization methods. Results show that solubility increases and the metastable zone width narrows with an increase in the evaporation temperature. At an evaporation temperature of 338.15 K, the controllability of the crystallization process improves and explosive nucleation does not easily occur. In this case, crystals with large average particle sizes, regular morphologies, and high crystallinity are obtained. With an increase in the Mg²⁺ concentration in the solvent, solubility decreases. The added Mg²⁺ covers the active nucleation sites, thus hindering the nucleation of ammonium sulfate and widening the metastable zone width. At a Mg²⁺ concentration of 0.9 g L⁻¹ or higher, Mg²⁺ covers the active surfaces of the grains. This inhibits normal crystal growth and hinders the nucleation and growth of ammonium sulfate crystals, so the crystallization amount of ammonium sulfate significantly reduces.

The wet dissolution process of lime is an effective approach for synthesizing calcium hydroxide. Process parameters and additives exert influence on the product particle. Among the process parameters, lime particle size, reaction temperature, and time have a significant impact on product particle size, followed by liquid-solid ratio and stirring speed. The experiment proved that reaction time affects product particle size by affecting the crystal growth, while other process parameters affect the particle size by affecting the ion diffusion behavior. In terms of inorganic additives, Ca(OH)₂ has minimal effect on product particle size; however, NaOH and CaCl₂ can significantly enhance it with a greater dose leading to a larger increase. The experiment proved that Ca(OH)₂, NaOH, and CaCl₂ influence particle size through their impact on ion diffusion behavior. Regarding organic additives, soluble starch exhibits the greatest effect on product size followed by triethanolamine and polyvinylpyrrolidone K30. The experiment proved that soluble starch, triethanolamine, and polyvinylpyrrolidone K30 affect product particle size by influencing its crystallization position. Finally, an ultrafine slurry of calcium hydroxide was prepared using the lime wet digestion method based on the aforementioned research, with particle size distribution characterized by D10, D50, and D90 values of 0.303, 1.750, and 4.534 µm respectively.

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.