Determination of thermodynamic properties of Ag3SBr superionic phase using EMF technique

Abstract

Triangulation of the Ag–S–Br system in the Ag–S–AgBr section is carried out using the methods of physico-chemical analysis. The temperature dependence of EMF of the electrochemical cell of C|Ag|Ag3GeS3Br|D|C glass is studied in the range of 340–430 K (C are inert (graphite) electrodes; Ag, D are the cell electrodes; D is the equilibrium composition of the Ag3SBr–S–AgBr phase region; Ag3GeS3Br glass is the membrane with purely ionic (Ag+) conductivity). Equations E(T) are used to calculate the values of thermodynamic functions of the Ag3SBr phase that is in equilibrium with silver bromide and sulfur (T < 379.34 K) and in equilibrium with silver bromide and the liquid phase (T > 379.34 K). The values of thermodynamic functions of phases Ag3SI, Ag3SBr, and Ag3TeBr in the standard state are compared. The effect of chalcogen ↔ chalcogen and halogen ↔ halogen replacement in the anionic sublattice on the values of thermodynamic functions of phases is analyzed.