On the glass-crystal transformation kinetics in materials which fulfil the conditions of "site saturation". Application to the crystallization of some alloys of Sb-As-Se and Ge-Sb-Se glassy systems

A theoretical procedure has been developed for the kinetic study of the glass-crystal transformation under continuous heating regime in materials involving formation and growth of nuclei. The quoted procedure obtains an evolution equation with the temperature for the actual volume fraction transformed at non-isothermal reactions. In this procedure an extended volume of transformed material has been defined and spatially random transformed regions have been assumed in order to obtain a general expression of the actual volume fraction transformed as a function of the temperature using differential scanning calorimetry. The kinetic parameters of the quoted transformation have been deduced, assuming that the crystal growth rate has an Arrhenius-type temperature dependence, and the nucleation frequency is negligible, condition of "site saturation", and using the following considerations: the condition of maximum crystallization rate and the quoted maximum rate. The procedure developed has been applied to the analysis of the crystallization kinetics of some semiconducting alloys, prepared in our laboratory, corresponding to the Sb-As-Se and Ge-Sb-Se glassy systems, and which fulfil the condition of "site saturation". The obtained values for the kinetic parameters satisfactorily agree with the calculated results by the non-isothermal technique of maximum-value. This fact confirms the reliability and accuracy of the theoretical procedure developed.