The effect of material aging on crystallization kinetics of Se70Te30 glass

Abstract

The effect of long-term room-temperature degradation (up to 6 months) on Se70Te30 crystallization kinetics was investigated by differential scanning calorimetry in dependence on experimental conditions of the measurement—applied heating rate and particle size of the powdered material. In case of very fine powders massive amorphous-to-crystalline degradation occurred even at room temperature, indicating that the small powder grains have fully defects-imbued inner structure that accelerates crystal growth. The kinetic data obtained for the consequent crystallization of the remaining glassy matrix showed that the defects-based Johnson-Mehl-Avrami crystallization is under quasi-equilibrium conditions further accelerated towards autocatalytic mechanism. Coarse powders, on the other hand, exhibited primary degradation only in a surface layer of the powder grains. The main effect of the coarse powders aging was found to be associated with marked enhancement of crystal growth originating from volume-located nuclei—either a sub-Tg nucleation occurred during aging or some pre-existing nuclei were activated during this time (possibly via mechanical stresses arising from structural relaxation processes).