Thermal stability and crystallization kinetics study of some Se-Te-Ge glassy alloys

Thermal stability and crystallization kinetics of (Se85Te15)100 − xGex (x = 0, 2, 5 and 10) glasses have been studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD), optical microscopy (POM) and scanning electron microscopy (SEM). The variation of the glass transition temperature with composition suggests that a small amount of Ge ( ≤ 5 at.%) leads to an increase in the length of the Se-Te chains, whereas further enrichment in Ge (10 at.%) increases the number of Se-Te chains in the alloys. Thermal stability of these samples is discussed. For glassy alloys prone to crystallize, the emerging crystalline phase reflections correspond to h.c.p. Se(Te). Surface and bulk crystallization can be found and in both cases crystalline nuclei develop as spherulites. The activation energies for the glass transition and for crystallization have been calculated. The crystallization kinetics has been established and a discussion of the possible mechanisms involved in the crystallization process is presented.