Thermal transport near the glass transition in bulk As-Se glasses.

Abstract

We have carried out a detailed investigation of the thermal-transport properties of bulk ${\mathrm{As}}_{\mathrm{x}}$${\mathrm{Se}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$ glasses near their glass-transition temperatures, using the photoacoustic (PA) technique. Temperature dependence of the thermal diffusivity in several compositions of these glasses in the glass-forming region has been determined by measuring the PA amplitude and phase and their chopping-frequency dependencies. It is found that the PA amplitude has a minimum value and the phase has a maximum value at the glass-transition temperature ${T}_{g}$ in all the compositions. Correspondingly, the thermal diffusivity and conductivity have minimum values at ${T}_{g}$. Also, the temperature dependence of the optical energy gap ${E}_{0}$ in ${\mathrm{As}}_{\mathrm{x}}$${\mathrm{Se}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$ glasses has been determined by use of the PA technique. As expected, ${E}_{0}$ decreases with temperature but with no marked change at ${T}_{g}$, except for an increase in slope for the curves in the region.