THERMODYNAMIC PROPERTIES OF SILVER-GERMANIUM TELLURIDE

Abstract

Compounds of the argyrodite family with the general formula Ag8A IVX6 (AIV -Si, Ge, Sn; X-S, Se, Te) and phases based on them are valuable environmentally friendly functional materials exhibiting thermoelectric, photoelectric, optical and other properties. They also have ionic conductivity for Cu+ and Ag+ cations and are very promising for use as electrochemical sensors, electrodes, or electrolyte materials in devices for electrochemical energy conversion. The Ag-Ge-Te system in the Ag8GeTe6-GeTe-Te composition range was studied by EMF measurements of the concentration cells concerning silver electrode with the Ag4RbI5 solid electrolyte in the 300-400 K temperature interval. From the EMF measurements data, the partial molar function of silver in alloys was calculated. Based on the data on solid-phase equilibria, the potential-forming reaction responsible for these partial molar functions was determined, and the standard thermodynamic formation functions and the standard entropy of the Ag8GeTe6 compound were calculated. The obtained experimental results are compared with the available literature data.