Krykhovets' O. Phase equilibria and crystal chemical characteristics of the solid solutions and intermediate phases in the systems Ag2Se - BIII2Se3 - CIVSe2 (BIII - Ga, In; CIV - Ge, Sn).

The thesis contains the results of investigation of the interaction between components in quasiternary systems Ag2Se - In2Se3 - GeSe2 and Ag2Se - In2Se3 - SnSe2. Phase diagrams, polythermal and isothermal sections of quasibinary sestems and the projections of liquidus surfaces and space diagrams of quisiternary systems have been built. Limit compositions of solid solutions have been established; the existence of four ternary and two quaternary compounds has been confirmed and one ternary and two quaternary compounds have been found for forst time. Crystal structure of the Ag2In2GeSe6 compound, which is of a new type, has been studied by X - ray single crystal method. Lattice parameters of the other compounds have been determined by X - ray powder method.