Thermodynamic parameters of diffuse phase transitions in Ag2Te

A differential thermal analysis in vacuum and studies of the coefficients of electrical conductivity and thermal conductivity, and of the thermal emf are made in Ag2Te in the neighborhood of the structural phase transition. It is shown that these data can be used to calculate the switching factor L(T), determine the region in which the phases coexist within the transition, and calculate the thermodynamic parameters. Prior to and after the main phase transition, additional displacement transitions are observed. It is found that the phase transition takes place roughly according to the scheme alpha(385) (K)--> alpha(405)' (K)--> beta(420)' (K)--> beta(440K). The specific heat C-p, changes in entropy Delta S and transition enthalpy Delta H, as well as the minimum phase fluctuation volume V, and the heat Q of the phase transition are determined. It is shown that excesses of Te and Ag have almost no effect on the transition temperatures T-0, but have a substantial effect on the thermodynamic parameters. (C) 1998 American Institute of Physics. [S1063-7834(98)02709-9].