Glass transition kinetics and crystallization mechanism in Se90Cd8Bi2 and Se90Cd6Bi4 chalcogenide glasses

Abstract

Differential scanning calorimeter (DSC), under non-isothermal condition, was used to study the glass transition kinetics and the crystallization mechanism of Se90Cd8Bi2 and Se90Cd6Bi4 glassy alloys. Two approaches, namely Moynihan and Kissinger, were used to calculate the relaxation activation energy (Et) from the dependence of the glass transition temperature (Tg) on the heating rate (β). Results reveal that Et decreases with an increase in Bi content which indicates that thermal stability is improved. This is attributed to the formation of Se–Bi bonds which are stronger than Se–Cd bonds and heavily cross-link the structure. In addition, the kinetic analysis of the crystallization peaks was performed using Ozawa, Kissinger, Takhor and Augis–Bennett relations. The values of the crystallization activation energy (Ec) and Avrami exponent (n) of the two alloys were evaluated. The obtained values of Ec, calculated from the above mentioned relations, were found to be in good agreement while the average calculated values of Avrami exponent (n) are (2.3±0.1) for Se90Cd8Bi2 and (1.7±0.1) for Se90Cd6Bi4 which indicating that the crystal growth in the two alloys occurs in one dimension.