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 investigated using Sb-121 Mossbauer spectroscopy. The isomer shift both for sulfide and selenide vitreous alloys is 1.2-2.0 mm/s more positive than that for corresponding crystalline parents. The smaller s-electron density at the Sb-121 nucleus for glasses indicates a decrease of the antimony-chalcogen interatomic distances in comparison with those for crystalline materials. The isomer shift systematics and composition dependencies of the electric-quadrupole coupling constant, eQV(zz), and 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 case of Ag+ ion-conducting vitreous alloys, however, the antimony-chalcogen distances are governed by the silver content and do not depend on the Sb fraction of the glass. Geometric and topological disorder in the glass network is correlated with an increase of the electric-quadrupole coupling constants and values of the asymmetry parameter eta between 0.4 and 1.0.