Determining kinetic parameters for isothermal crystallization of glasses

Non-isothermal crystallization techniques are frequently used to determine the kinetic parameters for crystallization in glasses. The techniques are experimentally simple and quick, compared with isothermal techniques. However, the analytical models used for non-isothermal data analysis, that were derived from models originally developed for describing isothermal transformation kinetics, are fundamentally flawed. The present paper describes a technique for determining the kinetic parameters for isothermal crystallization in glasses, which eliminates most of the common problems that generally make the study of isothermal crystallization laborious and time consuming. In this technique, the volume fraction of a glass that is crystallized as a function of time during an isothermal hold was determined in a separate experiment using differential thermal analysis. The activation energy (345 +/- 10 kJ/mole) and Avrami parameter (0.89 +/- 0.09) for crystallization of Li2O.2SiO(2) glass determined by the present technique are consistent with the similar values reported in the literature.