A THEORETICAL STUDY ON THE NON-ISOTHERMAL CRYSTALLIZATION KINETICS. APPLICATION TO THE Sb_(0.16)As_(0.29)Se_(0.55) GLASSY ALLOY

摘要

A procedure has been developed for analyzing the glass-crystal transformation from differential scanning calorimetry (DSC) data under non-isothermal conditions. Considering the assumptions of extended volume and random nucleation, a general expression of the fraction crystallized has been obtained, as a function of the temperature for bulk crystallization. The kinetic parameters have been deduced, assuming that the crystal growth rate has an Arrhenius-type temperature dependence, and the nucleation frequency is either constant or negligible. The theoretical method described has been applied to the crystallization kinetics of glassy alloy Sb_(0.16)As_(0.29)Se_(0.55) with and without previous reheating. According to the study carried out, the values of the kinetic exponent, n, are: 3.1 for the as-quenched glass and 2.1 for the reheated glass. As n decreases with reheating, it is possible to state that the annealing causes the appearance of new nuclei. The phases at which the alloy crystallizes after the thermal process have been identified by X-ray. The diffractogram of the transformed material suggests the presence of microcrystallites of Sb_2Se_3 and AsSe, remaining in the amorphous matrix.