Observation of phase separation in some Se-Te-Sn chalcogenide glasses

Differential scanning calorimeter (DSC) and X-ray diffraction (XRD) techniques were employed here to investigate the glass transition behavior and crystallization kinetics of Se80-x Te20Snx (x=0.0, 2.5 and 5) alloys, which were prepared by the conventional melt quenching method. Two exothermic peaks have been observed in the DSC scans for the samples that contain Sn. Three crystalline phases (Se7.68Te0.32, SnSe and SnTe) were classified after heat treating the Se77.5 Te20Sn2.5 glass at temperature corresponding to the second crystallization peaks for 3 h. All the characteristic temperatures such as glass transition temperature (Tg), crystallization temperature (Tc) and crystallization peak temperatures (Tp) were found to depend on both the heating rate and the composition. This dependence has been used to deduce the activation energy of the glass transition (Eg), the activation energy of crystallization (Ec), the Avrami exponent (n), thermal stability and the fragility index (Fi).