Kinetic Analysis of Thermal Processes in Ag-As-S-Se System Based on DSC Measurements

Thermal properties of glasses from the system $Ag_x(As_{40}S_{30}Se_{30})_{100-x}$ for x=0, 0.5, 1, 3, and 5 at.% were investigated by differential scanning calorimetry. The DSC curves were obtained under non-isothermal conditions which allowed determination of the glass transition temperature $T_{g}$ (onset temperature), crystallization temperature $T_{p}$ (corresponding to the crystallization peak maximum), melting temperature $T_{m}$, crystallization enthalpy $H_{c}$, and melting enthalpy $H_{m}$. The DSC curves obtained at the same heating rate were analyzed in order to study the variation of glass transition temperature with Ag concentration. Observed $T_{g}$ shift toward higher values, with increase in the heating rate, is in agreement with the Lasocka equation. Samples with 3 at.% and 5 at.% Ag were further thermally treated at different heating rates with the aim of analyzing kinetic processes of crystallization. The Moynihan and Kissinger models were used to calculate the activation energy of glass transition and activation energy of crystallization. For the samples that showed the crystallization processes an assessment of the thermal stability was done based on different criteria.