The phase equilibria in the Ag2S–Ag8GeS6–Ag8SnS6 system

Abstract

The phase equilibria in the Ag2S–Ag8GeS6–Ag8SnS6 system were investigated experimentally by means of differential thermal analysis (DTA), X-ray diffraction (XRD) techniques, scanning electron microscopy (SEM) and electromotive force (EMF) measurements of the concentration chains with Ag4RbI5 solid electrolyte. The phase diagram of the boundary Ag8GeS6–Ag8SnS6 system, two isopleth sections as well as liquidus surface projection of the Ag2S–Ag8GeS6–Ag8SnS6 system was plotted. The continuous solid solution series between low and high temperature modifications of both initial compounds were found along the boundary Ag8GeS6–Ag8SnS6 system. It was found that the Ag2S–Ag8GeS6–Ag8SnS6 system is quasi-ternary plane of the quaternary system and relates to monovariant eutectic type. The partial molar thermodynamic functions (ΔG‾,ΔH‾,ΔS¯) of silver were calculated for the LTM-Ag8Ge1−xSnxS6 (for x=0.2; 0.4; 0.6; 0.8) solid solution based on the results of the EMF measurements.