Effect of wide range of heating rate on the crystallization kinetic parameters of Se 77Te 20Sb 3 glass

Abstract

The kinetic parameters of glassy Se 77Te 20Sb 3 under non-isothermal conditions are analyzed by the model-fitting and model-free approaches. Differential scanning calorimetry (DSC) technique was used to study the kinetics of amorphous to crystalline transformation for Se 77Te 20Sb 3 glass using a wide range of heating rates (4–90 K/min). The analysis of the present data shows that the activation energy of crystallization is not constant but varies with the degree of conversion and hence with temperature. The reaction model that may describe the crystallization process of the Se 77Te 20Sb 3 glass is model A2 (Avrami–Erofeev with n = 2) for heating rates 4–30 K/min. While, the reaction model A3/2 (Avrami–Erofeev with n = 1.5) is a proper model that may describe crystallization process of the present glass for higher heating rates (35–90 K/min). The crystallization mechanisms examined using the local Avrami exponents indicate that one mechanism (two-dimensional growth) is responsible for the crystallization process for heating rates (4–30 K/min) and two mechanisms (one- and two-dimensional growth) are working simultaneously during the amorphous–crystalline transformation of glassy Se 77Te 20Sb 3 for higher heating rates (35–90 K/min). A good agreement between the experimental and the reconstructed ( α– T) curves has been achieved. The transformation from amorphous to crystalline phase in glassy Se 77Te 20Sb 3 demonstrates complex multi-step involving several processes.