A Kinetic Analysis on Non-Isothermal Glass-Crystal Transformation in Glassy Semiconductors. Application to the Sb_0.16As_0.29Se_0.55 Alloy

In the present work, a kinetic analysis on glass-crystal transformation from differential scanning calorimetry (DSC) data under non-isothermal condition is described. A method has been developed for analyzing the evolution with time of the volume fraction crystallized and for calculating the kinetic parameters at non-isothermal reactions in materials involving formation and growth of nuclei. 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 in 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 procedure described has been applied to the crystallization kinetics of glassy alloy Sb_0.16As_0.29Se_0.55 with and without previous reheating. According to the study carried out, the n-values have been found: 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 diffraction. The diffractogram of the transformed material suggests the presence of microcrystallites of Sb₂Se₃ and AsSe remaining in a residual amorphous matrix.