SB-121 MOSSBAUER STUDY OF INSULATING AND ION-CONDUCTING ANTIMONY CHALCOGENIDE-BASED GLASSES

The local environment of antimony in As2S3-Sb2S3, AgI-Sb2S3, As-Sb-Se and Ag-As-Sb-Se glasses, glassy/crystalline alloys and crystals is inv estigated using Sb-121 Mossbauer spectroscopy. The isomer shift both f or sulfide and selenide vitreous alloys is 1.2-2.0 mm/s more positive than that for corresponding crystalline parents. The smaller s-electro n density at the Sb-121 nucleus for glasses indicates a decrease of th e antimony-chalcogen interatomic distances in comparison with those fo r crystalline materials. The isomer shift systematics and composition dependencies of the electric-quadrupole coupling constant, eQV(zz), an d the asymmetry parameter, eta, shows that in As2S3-Sb2S3 and As-Sb-Se insulating glasses an isomorphous substitution of arsenic by antimony occurs accompanied by an increase of interatomic distances. In the ca se of Ag+ ion-conducting vitreous alloys, however, the antimony-chalco gen distances are governed by the silver content and do not depend on the Sb fraction of the glass. Geometric and topological disorder in th e glass network is correlated with an increase of the electric-quadrup ole coupling constants and values of the asymmetry parameter eta betwe en 0.4 and 1.0.