An alternative theoretical procedure to analyze the non-isothermal glass-crystal transformation kinetics: crystallization of the Sb0.13As0.35Se0.52 glassy semiconductor

Abstract

A procedure has been developed for analyzing the evolution with temperature of the actual transformed volume fraction and for calculating the kinetic parameters at non-isothermal reactions in materials involving formation and growth of nuclei. By considering the assumptions of extended volume and spatially random nucleation, as well as, assuming that both the nucleation frequency and the crystal growth rate depend on time as a power law, an equation of the extended transformed volume fraction has been obtained as a function of the temperature. From the quoted equation and according to the Jhonson–Mehl–Avrami model, it has been deduced an expression for the actual transformed volume fraction. The theoretical procedure described has been applied to the non-isothermal crystallization kinetics of the Sb0.13As0.35Se0.52 glassy alloy, with and without previous reheating, using DSC technique. In accordance with the study carried out, it is possible to state that the reheating did not cause the appearance of nuclei, but that the as-quenched material already contains a sufficient number of them. Likewise, it has been analyzed the variations of the kinetic exponent and the activation energy with the temperature. This analysis suggests that the transformation cannot be described by a mechanism of single-step, which demonstrates a mechanism of complex multi-step. Moreover, the experimental curve of the transformed fraction shows a satisfactory agreement with the theoretical curve corresponding to the considered procedure, confirming the reliability of the same to analyze the transformation kinetics of the studied alloy. The phase at which the alloy crystallizes after the thermal process has been identified by X-ray diffraction. The obtained diffractogram suggests the presence of micro crystallites of Sb2Se3, remaining an additional amorphous matrix.