Kinetics of the glass transition in As22S78 chalcogenide glass: Activation energy and fragility index

Differential scanning calorimetry (DSC) has been used to probe the dynamics of the glass transition in As22S78 chalcogenide glass. Non-isothermal measurements were performed at different heating rates (5–35 K min−1). The experimental result of this kinetic glass transition phenomenon was analyzed on the basis of the relaxation process occurring in the transition temperature range. The activation energy of the glass transition was determined from the heating rate dependence of the glass transition temperature. The fragility index m of the glass was estimated from the measurements of the activation energy of the relaxation process, which characterizes the glass transition. Different kinetic methods as well as isoconversional methods were used. Isoconversional analysis of the experimental data shows that the activation energy of glass transition process is varying with the degree of transformation (and hence with temperature) from the glassy to the supercooled phase.