CALORIMETRIC STUDY OF PHASE TRANSITIONS OF Ag₈SiS₆(Se₆) COMPOUNDS

Abstract: Polymorphic transitions in the Ag₈SiS₆ and Ag₈SiSe₆ compounds were studied by differential scanning calorimetry (DSC). Two samples of each compound with different sample weights in the range from 20 to 50 mg were selected for the studies, for which three DSC heating curves were recorded. Based on the DSC curves, the temperatures and enthalpies of phase transitions of the studied compounds from the low-temperature rhombic modification to the high-temperature cubic modification were determined. The data obtained on all DSC heating curves for each sample did not exceed 2%. The entropies of these transitions (ΔSp.t.) were calculated from the values ​​of heats and temperatures. It was shown that the values ​​of ΔSp.t. both compounds have anomalously high values, which can be explained by the complete delocalization of silver ions in the cation sublattice during the transition from low-temperature modifications to high-temperature cubic ion-conducting phases.