29Si and 27Al MASS-NMR studies of Li 2S + Al 2S 3 + SiS 2 glasses

Abstract

The first investigation of the preparation, characterization, and local structure of Li 2S + Al 2S 3 + SiS 2 glasses is reported. Glass-forming range, T g, infrared spectra and 27Al and 29Si MASS-NMR have been measured. The glass-forming range, although more extensive than that of the Li 2S + SiS 2 binary, is still quite restricted and limited to compositions containing at least 40 mol% SiS 2 and at most 60 mol%. The glass transition temperature shows a monotonic increase with substitution of Al 2S 3 for SiS 2 and Al 2S 3 for Li 2S. Highest T gs are measured for glasses with maximum mol% Al 2S 3. This observation is used to suggest that Al 2S 3 is reducing the number of non-bridging sulfur ions in the glass. Like the 29Si MASS-NMR of the binary Li 2S + SiS 2 glasses, the spectra are insensitive to composition. This observation suggest that the extent of edge-sharing rather than non-bridging sulfurs is the dominant effect on chemical shift. The 29Si MASS-NMR experiments show that adding aluminum to Li 2S + SiS 2 glasses decreases edge-sharing SiS 4 tetrahedra. 27Al MASS-NMR experiments show that aluminum goes into tetrahedral coordination in these glasses, and DSC measurements confirm this coordination.