Phase transformation kinetics and related thermodynamic and optical properties in chalcogenide glasses

• Published in: Journal of non-crystalline solids 2004-10, Vol.345-346 (Complete), p.161-168
• Main Author: Saxena, N.S.
• Format: Article
• Language: English
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2004.08.016

This talk presents the results of kinetic studies of glass transition and crystallization in glassy Se85−xTe15Sbx (x=2, 4, 6,8 and 10) using differential scanning calorimetry (DSC). In addition the thermodynamic properties of these glasses in the transformation range of temperature have been studied. The glass transition region has been investigated in terms of the activation energy of the glass transition and the dependence of glass transition temperature, Tg, on composition and heating rates. The growth kinetics and dimensionality have been investigated using three different models viz: Kissinger, Matusita and Ozawa. On the basis of the experimental results on phase transformations in these glasses, thermodynamic parameters like the entropy difference between different frozen states in the glassy region, the difference of Gibbs free energy between two phases and the enthalpy released during crystallization have been determined. Thermal transport properties like thermal conductivity and thermal diffusivity measured by author and his group in these glasses employing transient plane source (TPS) technique at room temperature and normal pressure [Phys. Stat. Sol. (a) 189 (2002) 197] have also been given. An effort has also been made to determine the optical band gap in these glasses from reflection spectra in the wavelength region between 300 and 800nm. It has been found from the experimental results and theoretical calculations of thermodynamic properties that Se81Te15Sb4 is the most stable glass against crystallization. The maximum values of thermal conductivity and thermal diffusivity and the minimum value of band gap in these glasses are also suggestive of the fact that glass becomes chemically ordered and more stable for this composition of Sb as compared to other concentrations.