Thermodynamic study of the Ag-Tl-Se system using the EMF method with AG4RbI5 as a solid electrolyte

Abstract

The Ag-Tl-Se ternary system in the composition region Ag2Se-Tl2Se-Se was studied in the temperature range 300–450 K by measuring the electromotive force (EMF) in a concentration cell containing a silver electrode and Ag4RbI5 as a solid electrolyte. A previously constructed solid-phase equilibria diagram of this system that included the ternary compounds AgTlSe, Ag3TlSe2, and Ag7TlSe4 was confirmed. The EMF measurements allowed the partial molar functions $$ \left(\Delta \overline{G},\Delta \overline{H},\Delta \overline{S}\right) $$ of silver in some phase regions of the Ag2Se-Tl2Se-Se subsystem to be calculated. Using the solid-phase equilibria diagram, the potential-forming reactions were defined and the standard thermodynamic functions of formation and the standard entropy values of the ternary compounds mentioned above were calculated. Besides experimental results, data reported in the literature for thermodynamic functions of TlSe as well as the standard entropy values of silver and selenium were used in the calculations. The results of the calculations were compared with relevant data in the literature. The results confirmed that it is possible to study the thermodynamics of silver-containing complex systems using this modified EMF method, even if the system contains a more electropositive component than silver.