R. G. Grebenshchikov

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.

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.

Phase Relationships in the Section CaGeO3-BaSiO3 of the Ternary Mutual System CaO, BaO∥SiO2, GeO2

Phase relationships in the section CaGeO3-BaSiO3 in the range 1000-1500°C were studied. Samples were prepared by a solid-phase procedure. The phase relationships were studied by X-ray phase, differential thermal, and crystal-optical (with immersion specimens) analyses and by the annealing-quenching technique. The phase diagram of the system CaGeO3-BaSiO3 was constructred. A discrete variable-composition berthollide phase crystallizing in the walstromite structural type was revealed. No solid solutions based on the extreme members of the system were found. The diagram of phase equilibria in the edge sections of the concentration tetragon CaSiO3-4CaGeO3-BaGeO3-BaSiO3 is presented, and the solubility boundaries are schematically shown for the solid solutions existing in this system at 1200°C.

Subsolidus Phase Relationships in the Er2O3-Rh2O3 System

The Er2O3-Rh2O3 system was studied by the annealing and quenching method using X-ray phase, thermal, and chemical analyses. A schematic subsolidus diagram of phase relationships was constructed.