Crystallization of Ge0.08Sb0.15Se0.77 glass studied by DSC

Abstract

A theoretical method has been considered for deriving the evolution equation with time of the actual volume fraction transformed, for integrating the above mentioned equation under non-isothermal regime, and for deducing the kinetic parameters of the glass–crystal transformations in solid systems where a large number of nuclei already exists and no new nuclei are formed during the thermal treatment. In this case, it is assumed that the nuclei only grow, ‘site saturation’, during the thermal process. By defining an extended volume of transformed material and assuming spatially random transformed regions, a general expression of the extended volume fraction has been obtained as a function of the temperature. Considering the impingement effect and from the above mentioned expression the actual volume fraction has been deduced. The kinetic parameters have been obtained, assuming that the reaction rate constant is a time function through its Arrhenian temperature dependence. The theoretical method considered has been applied to the crystallization kinetics of the Ge0.08Sb0.15Se0.77 glassy alloy with and without previous reheating. According to the study carried out, it is possible to state that in the considered alloy the nuclei were dominant before thermal analysis, and therefore the reheating did not appreciably change the number of pre-existing nuclei in the material, which constitutes a case of ‘site saturation’.