Thermodynamic Study of Cu2GeS3 and Cu2–xAgxGeS3 Solid Solutions by the EMF Method with a Cu4RbCl3I2 Solid Electrolyte

Abstract

The Cu₂GeS₃–Ag₂GeS₃ system was studied by the EMF method with a Cu₄RbCl₃I₂ solid electrolyte in the temperature range 300–380 K. The formation of wide regions of solid solutions from the starting compounds in this system was confirmed. The partial thermodynamic functions (ΔG, ΔH, ΔS) of copper in alloys were calculated from the equations of the temperature dependences of EMF. The current-forming reactions were determined based on the schematic diagram of solid-phase equilibria in the Cu–Ag–Ge–S system and used to calculate the standard thermodynamic functions of formation and the standard entropies of the compound Cu₂GeS₃ and solid solutions Cu_2–xAg_xGeS₃ (х = 0.2, 0.4, 0.6, 1.6, and 1.8) and the thermodynamic functions of mixing of the latter from ternary compounds.