Phase Equilibria in the Cu2Se–Cu8SiSe6–Cu8GeSe6 System

Phase equilibria in the Cu2Se–Cu8SiSe6–Cu8GeSe6 area of the Cu2Se–SiSe2–GeSe2 system have been studied using differential thermal analysis (DTA), X-ray powder diffraction analysis (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDX). The results served to plot a Т–х diagram of the Cu8SiSe6–Cu8GeSe6 boundary system, a series of polythermal sections, and a 300-K isothermal section of the phase diagram and a liquidus surface projection for the title system. The primary crystallization and homogeneity fields of phases, and the characters and temperatures of invariant and monovariant equilibria have been determined. In the Cu8SiSe6–Cu8GeSe6 boundary system, continuous solid solutions have been found to exist between the high-temperature phases of the terminal compounds and extensive homogeneity area based on their low-temperature phases were found. The crystal lattice types and unit cell parameters have been determined for the terminal compounds and both phases of solid solutions using X-ray powder diffraction data. The prepared phases of variable composition are of interest as environmentally friendly functional materials.