On the thermal properties of Ag$_2$Te and Ag$_2$Se in the region of the phase transition

A setup is developed for measuring the thermal properties of Ag$_2$Te and Ag$_2$Se near the main phase transition and in the region of it in high vacuum. The samples are of stoichiometric composition with an excess of Ag, Te, and Se. Differential thermal analysis is performed and the temperature differences across and along the samples are measured by the pulsed light method. Using data on the thermal diffusivity $a(T)$, the temperature dependence of the thermal conductivity $K = apc$ is determined, where $p$ is the density and $c$ is the specific heat. The measurement technique used allows us to establish that the main phase transitions are accompanied by intense heat release. New phase transitions before and after the main structural phase transition with heat absorption are found. According to the DTA data, in the Ag$_2$Te sample with an excess of Ag (0.25 at.%, $cn$ = 1.2 $\times$ 10$^{19}$ cm$^{-3}$) the phase transition at 365 K is also accompanied by heat absorption. Thus, it is established that all of the phase transitions in Ag$_2$Te and Ag$_2$Se are first-order.