Isoconversional Model of Kinetics of Thermally Induced Processes in Chalcogenide Glass Sb37S48I15

R.R. Raonić, N.M. Ćelić, S.R. Lukić-Petrović, G.R. Štrbac University of Novi Sad, Faculty of Sciences, Department of Physics, Trg Dositeja Obradovića 4, 21000 Novi Sad, Serbia

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In this paper, we have made isoconversional modeling and analyses of kinetics of thermally induced processes for Sb37S48I15 chalcogenide glass. The non-isothermal differential scanning calorimetry was used and for four different heating rates the corresponding curves were obtained with this method. The change in the apparent activation energy with the extent of conversion for three thermally induced processes (glass transition, crystallization and melting) was analyzed by using two different isoconversional methods - the isoconversional form of Kissinger model and the Vyazovkin method. The values of activation energy during the glass transition indicated the domination of cooperative movements of structural units while the decrease of this parameter with temperature (the extent of conversion) implied that these movements are becoming freer. The found dynamic fragility index value of m=23.2(10) indicated that significant configuration changes are not present near the glass transition temperature. Crystallizations of two structural units, SbSI and Sb2S3, were detected. For SbSI, the activation energy increased from Eα=103 eV for the extent of conversion of α=5% to Eα=162 eV for the extent of conversion of α=95%. This is related to the influence of the initial stage of parallel crystallization of the new structural unit Sb2S3. Activation energy for crystallization of Sb2S3 changed from Eα=140 eV to Eα=167 eV for the same values of the extent of conversion. A small change in energy indicates a volume nucleation with a constant number of nuclei. The isoconversional analysis of melting of SbSI has shown that the activation energy decreased with the extent of conversion from Eα=526 eV (α=4%) to Eα=341 eV (α=96%) and that it was not a single-step process. The results from both applied methods were in agreement.

DOI:10.12693/APhysPolA.140.235 topics: heat capacity, crystallization, glass transitions, differential thermal analysis (DTA)