S. K. Kuchaeva

Preparation and thermal transformations of nanocrystals in the LaPO4-LuPO4-H2O system

Powders of nanosized particles of individual and mixed lanthanum and lutetium orthophosphates are synthesized. The grain growth process is studied in the temperature range of 200–1100°C. Temperature and concentration regions of existence of the solid solutions based on hexagonal and monoclinic forms of LaPO4 as well as on tetragonal LuPO4 are determined.

Synthesis, mutual solubility, and thermal behavior of nanocrystals in the LaPO4-YPO4-H2O system

Nanopowders of lanthanum and yttrium orthophosphates have been synthesized. The growth of nanocrystals has been investigated in the temperature range 200–1100°C. The temperature-concentration limits of the existence of the solid solutions have been determined. The thermal behavior of the orthophosphates has been studied over the entire range of lanthanum and yttrium concentrations.

Crystallization and thermal transformations in nanocrystals of the YPO4-LuPO4-H2O system

Nanocrystals of yttrium lutetium phosphates of the general formula Y1−xLuxPO4 · nH2O are synthesized. The temperature dependence of the nanocrystal size is investigated in the range 200–1100°C. The formation of a series of continuous solid solutions belonging to the tetragonal crystal system is revealed, and the limits of their thermal stability are determined.

Phase Relationships in the NaPO3–Al2O3 Glass-Forming System

The phase formation is studied in the NaPO3–Al2O3 system (0–25 mol % Al2O3). It is shown that two individual compounds, namely, Na6Al2(P2O7)3 and Na3Al2(PO4)3, exist along the studied join. The phase diagram of the NaPO3–Al2O3 system (0–25 mol % Al2O3) is constructed. The phase separation phenomena are revealed in the melt.

Sequence of phase formation during solid-state synthesis in the Y2O3 BaO CuO system

The sequence of formation of phases in the solid state synthesis of the YBa2Cu3O7, Y2BaCuO5, BaCuO2, Y2Cu2O5 was studied using the methods of annealing, quenching, DTA, XRD and crystallooptical analysis in air in the range of temperatures 550–1100°. The starting mixtures consisted of Y2O3, CuO, a Ba component introduced as a carbonate, peroxide or nitrate. It was established that the formation of ternary compounds in the system proceeds as a multiple-step reaction involving intermediate phases and is determined by the nature of the Ba containing component. The phase formation in the Y2O3BaOCuO system is described by several chemical reactions.

Nanopowders of orthophosphate LaPO4-YPO4-H2O system and ceramics based on them

Nanopowders of orthophosphate LaPO4-YPO4-H2O system have been synthesized via the solgel method, and the limits of the mutual solubility of components have been specified through the calculation of the parameters of the unit cell. The dense ceramics were prepared based on the La1 − xYxPO4 · nH2O nan-opowders at 1000 and 1200°C. The porosity, microhardness, and bending strength of the ceramics were determined, and the dependence of the microhardness on the calcination time was established. The thermal behavior of the samples was studied by dilatometric method and the thermal coefficient of linear expansion of the ceramics was estimated.

Phase equilibria in the system CaSiO3-BaGeO3

The phase relationships in the system CaSiO3-BaGeO3 were studied and its phase diagram was constructed.

Synthesis and study of novel catalysts based on hollandite K2Ga2Ti6O16

The results of experimental studies of synthesis of the hollandite phase K2Ga2Ti6O16 using initial mixtures of different dispersion compositions obtained by two methods, i.e., mechanical dispersion (MD) (followed by solid-phase sintering) and sol-gel method (Pechini method, MP), are reported. The catalytic properties of the obtained materials in the reactions of carbon monoxide (CO) and hydrogen (H2) oxidation have been determined. It has been demonstrated that an increase in the catalytic activity in the CO oxidation reaction is observed on the samples obtained using the sol-gel method, in which the hollandite phase content is higher and crystallization is more complete. The samples obtained using the MD method are characterized by a low porosity and activity in comparison with those produced by the Pechini method.

Subsolidus phase relations in the Gd2O3-Rh2O3 system

The Gd2O3-Rh2O3 system is studied using the anneal-and-quench technique, X-ray powder diffraction, thermal analysis, and chemical analysis. A schematic subsolidus phase diagram is designed. One double oxide of composition GdRhO3 is found to exist. It was characterized using some physicochemical methods.

Isomorphism and Phase Relationships in the Systems of Metagermanosilicates of Alkaline-Earth Metals

A comparative analysis of the phase relationships in the ternary mutual systems CaO,SrO‖SiO2, GeO2; CaO,BaO‖SiO2,GeO2; and SrO,BaO‖SiO2,GeO2 was performed and the crystal-chemical properties of the phases crystallizing in them were determined.