An alternative treatment of non-isothermal heterogeneous transformations -: Application to the crystallization of Ge0.13Sb0.23Se0.64 alloy

Continuous heating differential scanning calorimetry is frequently employed to study the kinetics of transformation reactions and, in particular, the crystallization of the glassy alloys. Such data are analyzed by the Kissinger method, which was originally derived for the study of homogeneous reactions. Although the consensus in the literature, over several decades, was that such applications (i.e. to heterogeneous solid state transformations) of the Kissinger method are not valid, nevertheless, by assuming that the transformation products and mechanism do not change with temperature, it is possible a valid application of Kissinger method to non-isothermal heterogeneous transformations. In this work, the principal objections to these applications are addressed and bearing in mind the quoted assumptions alternative derivations of theoretical results are provided. These results demonstrate that the Kissinger method is valid for heterogeneous reactions of the type described by the Johnson-Mehl-Avrami-Kolomogoroff equation in the isothermal case. Isothermal and continuous heating data on the crystallization of Ge0.13Sb0.23Se0.64 semiconducting alloy are presented. These experimental results and the discussion presented here help to clarify the effects of incubation time on the non-isothermal transformation kinetics and provide a further demonstration of the validity of the generalized Johnson-Mehl-Avrami-Kolomogoroff theory for the description of heterogeneous solid state transformations. (C) 2004 Elsevier B.V. All rights reserved.