Phase Equilibria and Thermodynamic Properties of Selected Compounds in the Ag–Ga–S–AgBr System for Modern Application in Energy Conversion Devices

The phase equilibria of the Ag–Ga–S–AgBr system in the part GaS–Ga₂S₅–AgBr–Ag₂S below 600 K were investigated by the modified electromotive force (EMF) method using the Ag⁺ catalysts as small nucleation centers of equilibrium phases. Division of the GaS–Ga₂S₅–AgBr–Ag₂S was carried out with the participation of the following compounds Ag₂S, GaS, Ga₂S₃, AgBr, Ag₉GaS₆, AgGaS₂, Ag₃SBr, Ag₃Ga₂S₄Br, and Ag₂₇Ga₂S₁₂Br₉. Reactions were performed by applying electrochemical cells (ECs) with the structure: (−) IE | NE | SSE | R{Ag⁺} | PE | IE (+), where IE is the inert electrode (graphite powder), NE is the negative electrode (silver powder), SSE is the solid-state electrolyte (glassy Ag₃GeS₃Br), PE is the positive electrode, R{Ag⁺} is the region of Ag⁺ diffusion into PE. The measured EMF and temperature values of ECs were used to determine the standard thermodynamic functions of the compounds Ag₃Ga₂S₄Br and Ag₂₇Ga₂S₁₂Br.