Phase equilibria in the Cu2SnSe3–Sb2Se3–Se system

Complex copper-tin and copper-antimony chalcogenides are of great interest for the development of new environmentally friendly and inexpensive thermoelectric materials. Recently, these compounds have been drawing more interest due to the possibility of increasing their thermoelectric performance with various cationic and anionic substitutions. In this article, we continued the study of multi-component systems based on the copper chalcogenides and presented the results of the study of phase equilibria in the Cu2SnSe3–Sb2Se3–Se system. The study was conducted using differential thermal analysis and powder X-ray diffraction. Based on the experimental data, a projection of the liquidus surface and three polythermal cross sections of the phase diagram were plotted. We determined the regions of primary crystallisation of the phases and the nature and temperatures of non-variant and monovariant equilibria. It was established that the liquidus surface consisted of two primary crystallisation regions based on Cu2SnSe3 and Sb2Se3 phases. The primary crystallisation region of elementary selenium was degenerate. A large immiscibility region of two liquid phases was found in the system

Phase equilibra in the Ag2S–Ag8GeS6–Ag8SiS6 system and some properties of solid solutions

Phase equilibria in the Ag2S–Ag8SiS6–Ag8GeS6 system were studied using differential thermal analysis and powder X-ray diffraction technique. Boundary section Ag8SiS6 – Ag8GeS6, liquidus surface projection, an isothermal section of the phase diagram at 300 K, and some polythermal sections of the studied system were constructed. The formation of continuous series of solid solutions between both crystalline modifications of the starting compounds was determined in the Ag8SiS6–Ag8GeS6 system. The liquidus surface of the Ag2S–Ag8SiS6–Ag8GeS6 system consists of two fields corresponding to the primary crystallization of the high-temperature modifications of the HT-Ag8Si1-xGexS6 and HTAg 2S phases. Lattice parameters for both modification of solid solutions were calculated based on powder X-ray diffraction data. The concentration dependence of lattice parameters obeys Vegard’s rule. The obtained new phases are of interest as environmentally safe materials with thermoelectric properties and mixed ionelectron conductivit