Optical gap of the glasses of the system As2S3-Tl2S-Sb2S3

The values of the optical band gap of As2S3-Tl2S-Sb2S3 glasses have been ex perimentally determined. They are found to decrease very differently with i ncreasing content of Sb2S3 and Tl2S, respectively. Addition of Sb2S3 Leads to a quasi-linear decrease of the band gap in agreement with the substituti on of Sb for As atoms. For glasses of the As2S3-Tl2S system the variations of the band gap as a function of the Tl2S concentration exhibit an unusual behaviour, which is also observed in the variations of the glass transition temperature. A drastic change in the variations of these two series of exp erimental data occurs at the Tl2S concentration of about 5% which is tentat ively explained from structural changes. (C) 2000 Elsevier Science S.A. All rights reserved.