Optical and Thermal Diffusivity Measurement of Ge-Se-Te Glasses by Photoacoustic Technique

The composition dependence of optical energy gap $(E_g)$ and thermal diffusivity (\alpha) in three sets of Ge-Se-Te glasses, namely, ${Ge}_x{Se}_{80-x}{Te}_{20}$ 5\leq x \leq40 ${Ge}_x{Se}_{75-x}{Te}_{25}$ 5\leq x \leq40 and ${Ge}_x{Se}_{65-x}{Te}_{35}$ 5\leq x \leq37.5 have been studied using photoacoustic technique. The variation of \alpha with an average coordination number (r) shows a change in the slope at (r) 2:4 and 2.67. ${E_g}$ shows a local maximum at (r) 2:67. The results are discussed on the basis of the topological and chemical threshold exhibited by covalent network glasses. The relative sensitivity of \alpha and ${E_g}$ to these phenomena is discussed