Effect of heating rate on the kinetics and mechanism of crystallization in amorphous Se85Te10Pb5 glasses

The kinetic parameters of amorphous Se85Te10Pb5 glasses were studied for nonisothermal and predicted isothermal conditions. Differential scanning calorimetry (DSC) was used to study the kinetics of the amorphous-to- crystalline transformation at heating rates in three regimes (3-15, 20-50 and 60-99 K min(-1)). Analysis of the obtained data shows that the activation energy of crystallization is not constant but varies with the degree of conversion and, hence, with temperature; thus, the variation depends on the heating rate. The Avrami exponents indicate that the mechanism of crystallization varies from one- to two- to three-dimensional growth at low, medium and high heating rates, respectively. The reduced reaction model was observed to follow the Avrami-Erofeev mechanism, but varies from A1.5 to A2 to A3 for the different heating-rate regimes. A good fit was achieved between experimental and predicted sigmoidal curves for the crystallization fraction with increasing temperature. (C) 2014 Elsevier B.V. All rights reserved.