Specific Heat of the Superionic Conductor Ag2TexS1-x

Specific heat capacities of “superionic conductor” Ag chalcogenides have been measured mainly for Ag 2 Te x S 1- x in the temperature range, 120–520 K. There is no indication of α-β transition except for x =0.1. Instead, a very broad peak of heat capacity is found at about 210 K for x =0.2–0.6. Using the method that H. Wiedersich and W. V. Johnston [J. Phys. Chem. Solids 30 (1969) 475] applied to RbAg 4 I 5 and assuming that the structure of Ag 2 Te x S 1- x is α-Ag 2 S or α-Ag 2 Te-like, the excess heat capacity can be explained fairly successfully as the transition of Ag + ions between two or more types of sites.