Preparation and characterization of glasses in the Ag2S+B2S3+GeS2 system

The glass forming range of the Ag2S + B2S3 + GeS2 ternary system was investigated for the first time and a wide range of ternary glasses were obtained. The Archimedes' method was used to determine the densities of the Ag-B-Ge glasses. The thermal properties of these thioborogermanate glasses were studied by DSC and TMA. The Raman, IR and NMR spectroscopy were used to explore the short-range order structure of the binary (Ag-B) and (Ag-Ge) and ternary (Ag-B-Ge) glasses. The results show the presence of bridging sulfur tetrahedral units, GeS4/2 and AgBS4/2, and trigonal units, BS3/2, in the ternary glasses. Non-bridging sulfur units, AgSGeS3/2 and Ag3B3S3S3/2 six membered rings, are also observed in these glasses at higher Ag2S modification levels because the further addition of Ag2S results in the degradation of the bridging structures to form non-bridging structures. The NMR studies show that Ag2S goes into the GeS2 subnetwork to form Ag3S3GeS1/2 groups before going to the B2S3 subnetwork. In doing so, it is suggested that B10S20 supertetrahedra exist in Ag2S + B2S3 and Ag2S + B2S3 + GeS2 glasses. Significantly B-S-Ge bonds form in the B2S3 + GeS2 glasses, whereas they appear to be absent in the ternary glasses. From these observations, a structural model for these glasses has been developed and proposed. (C) 2003 Elsevier B.V. All rights reserved.