COMPOSITION DEPENDENCE OF OPTICAL BAND-GAP AND THERMAL-DIFFUSIVITY OF AS-TE-SE GLASSES

The composition dependence of the optical band gap, E0, and thermal diffusivity, alpha, of As-Te-Se glasses, prepared by the conventional melt-quenching technique, have been determined using photoacoustic technique which is based on the detection of the acoustic signal produced when a modulated light beam is incident on the sample. The optical band gap is found to decrease with increase in As concentration, whereas thermal diffusivity shows a threshold maximum at 40 at.% of As content which is the stoichiometric compositions of the As-Te-Se system. The observed behaviour is explained on the basis of chemical bonding between the constituents and the idea of rigidity percolation in covalent random networks.