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Abstract: Differential scanning calorimetry (DSC) measurements were performed to investigate the kinetics of the structural relaxation in aged and unaged (rejuvenated) As x Se100−x glasses with 0≤x≤40. The activation energy of the glass transition (E a ) of the aged and rejuvenated glasses was determined from the variation of the glass transition temperature (T g ) with the heating rates (β). Significant effect of prolonged aging of the glasses on the values E a was observed. Evidence of transition from floppy to rigid phase is presented. The observed significant physical aging in samples with composition x<40 indicates the absence of the intermediate phase. The compositional dependence of T g for aged and rejuvenated data was analyzed using the stochastic agglomeration theory. [Copyright &y& Elsevier]

Abstract: The kinetics of crystallization in a-Se73.2Te21.1Sb5.7 were determined at different heating rates (2–99K/min) using differential scanning calorimetric (DSC) technique. It is evident from this study that the effective activation energy associated with crystallization, E c in a-Se73.2Te21.1Sb5.7 is not constant but heating rate dependent. Attempt is made to explain this variation in terms of recent theoretical models based on the concept of variable effective activation energy. Using isoconversional method, the temperature dependence of E c was determined. It is shown here that the apparent variation of E c with the heating rate is a result of this temperature dependence. It is also shown that the JMA-based models (Kissinger model etc.) which assume constant effective activation energy show clear deviation from linearity giving at least two values of effective activation energy. [Copyright &y& Elsevier]