THERMAL-STABILITY AND CRYSTALLIZATION KINETICS STUDY OF SOME SE-TE-GEGLASSY ALLOYS

Thermal stability and crystallization kinetics of (Se85Te15)(100-x)Ge- x (x = 0, 2, 5 and 10) glasses have been studied using differential sc anning calorimetry (DSC), X-ray diffraction (XRD). optical microscopy (POM) and scanning electron microscopy (SEM). The variation of the gla ss transition temperature with composition suggests that a small amoun t of Ge (less than or equal to 5 at.%) leads to an increase in the len gth of the Se-Te chains, whereas further enrichment in Gt: (10 at.%:lj 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(T e). Surface and bulk crystallization can be found and in both cases cr ystalline nuclei develop as spherulites. The activation energies for t he 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 present ed. (C) 1997 Elsevier Science S.A.