STRUCTURAL TAILORING OF SILICON CHALCOGENIDE GLASSES - COMPOSITIONAL CONTROL OF EDGE-SHARING UNITS AS MONITORED BY HIGH-RESOLUTION SI-29 SOLID-STATE NMR

29Si MAS-NMR data provide strong evidence for the presence of edgesharing tetrahedra in non-oxide chalcogenide glasses derived from SiS2 and SiSe2. The spectra show three distinct peaks which have been assigned on the basis of suitable model compound studies. It is further shown that the fraction of edge-sharing can be controlled by compositional parameters. In glassy SiSe2 both the presence of excess selenium and additional network formers such as phosphorus selenide are shown to diminish the degree of edge-sharing due to the formation of Si-Se-Se or Si-Se-P bonds. In glassy SiS2 a similar effect can be accomplished by a network modifier such as Li2S. In the latter case, the creation of nonbridging chalcogen atoms is accompanied by a concomitant decrease of edge-sharing tetrahedra. © 1990 J.C. Baltzer A.G. Scientific Publishing Company.