Structural and calorimetric studies of two crystallization stages of Ag10As30S60 glassy alloys

The structure of the as-prepared and thermal annealed Ag10As30S60 chalcogenide glass is characterized using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) curves recorded at four different heating rates are analyzed to determine the glass and crystallization transition temperatures, thermal stability and enthalpy release. Two separated crystallization peaks are observed in the DSC curves. XRD results indicate the precipitation of AgAsS4 crystal phase is responsible for the first peak. Numerous phases with S8 dominant phase are accountable for the second peak. The crystallization kinetics such as the activation energy for the crystallization (Ec), the frequency factor (Ko) and the crystallization rate constant K are determined for each crystallization stage. The results show that the crystallization rate constant for the first crystallization stage is about six times larger than that of the second crystallization step.