Vol 59, No 1 (2023)

Crystallization kinetics of 30-nm-thick amorphous TlIn_1–хSn_xSе₂ films produced by thermal evaporation under high vacuum in a dc electric field E = 3000 V/cm have been studied by kinematic electron diffraction. The results demonstrate that the formation of the crystal structure of the amorphous films during heat treatment follows Avrami–Kolmogorov relations. Kinetic curves of the phase transformation demonstrate the effect of an electric field on the temperature range of film crystallization and on the activation energies for nucleation and subsequent nucleus growth. The total activation energy for the crystallization process has been determined to be Etotal = 44.92 kcal/mol. The observed diffraction lines of the polycrystalline TlIn_0.93Sn_0.07Sе₂ films in their kinematic electron diffraction patterns can be indexed in tetragonal symmetry (sp. gr.  = \( D_{{4h}}^{{18}} \)-I4/mcm [12]) with unit-cell parameters a = b = 0.8358 nm and c = 0.7086 nm. After storage of the films in vacuum at room temperature for more than two months, no changes were detected in their quality or diffraction pattern.

We have grown single crystals of the Pb0.75Sn0.25Тe solid solution containing up to 1.0 at % hyperstoichiometric Sn and produced metal–semiconductor structures based on the crystals with the use of Bi + Sn and In + Ag + Au eutectics. The effect of annealing on their electrical properties has been studied in the temperature range ~77–300 K. We assume that, filling vacancies in the Pb and Sn sublattices of the crystals, small amounts of excess Sn atoms reduce carrier concentration n, causing an increase in the resistivity ρ of the crystals and the specific contact resistance rc of the structures. High Sn concentrations lead to the formation of additional donor centers in the crystals, increasing n and, accordingly, reducing ρ and rc.

Properties of a delphinidin complex with silicon carbide nanoparticles have been studied by optical methods. Electron microscopy data have been used to determine the phase composition of silicon carbide samples. A comparative analysis of the absorption spectra of solutions of delphinidin and delphinidin with silicon carbide nanoparticles has shown a marked increase in light absorption in the presence of the nanoparticles. The observed large increase in absorbance attests to a considerable adsorption of delphinidin molecules on the surface of silicon carbide nanoparticles. Combining delphinidin with silicon carbide nanoparticles improves the performance of Grätzel cells compared to the sensitizer without nanoparticles. The addition of silicon carbide nanoparticles to the dye increases the power and efficiency of the Grätzel cell.

This paper reports the use of a differential dissolution stoichiographic method for determining the phase composition of catalysts for ammine borane hydrolysis and hydrothermolysis [1, 2]. Cu1–xFe2+xO4 copper ferrite samples were prepared using layer-by-layer combustion, dried, and then calcined at different temperatures. We describe conditions that make it possible to detect and quantitatively determine various phases in the composition of amorphous and crystalline materials with the spinel structure and compare differential dissolution and X-ray diffraction results.

Interactions in the V2O5–AlN system have been studied using chemical analysis, X-ray diffraction, and thermal analysis in combination with mass spectrometry. The results demonstrate that heating mixtures with AlN/V2O5 molar ratios ≥2.33 to above 1100°C leads to the formation of the vanadium nitrides V2N, VN0.81, and VN among condensed reaction products. No formation of solid solutions of aluminum in vanadium or vanadium aluminides during heating has been detected in the temperature range studied. Chemical interaction of V2O5 with AlN meets Baikov’s transformation sequence principle: V2O5 → VO2 → V4O7 → V3O5 → V2O3 → VO → V.

We have studied the process and products of thermal dehydration of highly dispersed monoclinic AlРO4⋅2Н2О prepared by crystallization from an aluminum phosphate solution at 95–97°C and demonstrated the influence of isothermal or polythermal heat treatment on the formation of AlPO4 polymorphs similar in structure to α-quartz or tridymite. The formation of these phases has been shown to be related to changes in the oxygen coordination of aluminum as a result of the detachment of highly polarized molecules of water of crystallization in the composition of AlРO4⋅2Н2О. We have assessed the electrorheological (ER) activity of AlPO4 as a disperse phase of electrorheological fluids, with a weight fraction from 10 to 20%, and found out how AlPO4 preparation conditions influence the shear stress of the electrorheological fluids in electric fields from 3.5 to 4.0 kV/mm. Suspensions containing tridymite AlPO4 particles prepared under isothermal conditions have been shown to exhibit a stronger ER effect, at a level from 420 to 620 Pa. The ER activity of AlPO4 has been shown to increase with increasing heat treatment temperature and time, which is attributable to the formation of a more defect-rich particle surface due to intrinsic thermal disorder.

NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0 ≤ x ≤ 1.0) layered perovskites have been prepared by solid-state reactions and their crystal structure, microstructure, and thermal and electrical properties have been studied. The materials with x ≤ 0.4 have a tetragonal structure (sp. gr. P4/mmm) and those in the range 0.6 ≤ x ≤ 1.0 have a cubic structure (sp. gr. Pm3m) and are p-type semiconductors, but with increasing temperature the behavior of their electrical conductivity changes to metallic one as a result of labile oxygen (δ) release, accompanied by an increase in their linear thermal expansion coefficient from (15.1–16.2) × 10–6 to (18.9–23.5) × 10–6 К–1. Increasing the degree of strontium substitution for barium reduces the unit-cell parameters and thermoelectric power of the NdBa1–xSrxFeCo0.5Cu0.5O5+δ solid solutions and increases their electrical conductivity. We have evaluated activation energy for electrical transport processes, weighted charge carrier mobility, and charge carrier concentration in the perovskites and demonstrated that these parameters vary nonmonotonically with the cation composition of the materials, having extrema in the region of the tetragonal-to-cubic structural phase transition.

A Li3Ba2Gd3(MoO4)8:Er3+ phosphor in the Li2MoO4–BaMoO4–Gd2(MoO4)3 system has been synthesized (scheelite-like structure, sp. gr. C2/c) and its IR absorption and luminescence properties have been studied. The synthesized phosphor has been characterized by X-ray diffraction, differential thermal analysis, and IR spectroscopy.