Glass formation in and structural investigation of Li2S + GeS2+ GeO2 composition using Raman and IR spectroscopy

Abstract Li 2 S + GeS 2 + GeO 2 ternary glasses have been prepared and a wide glass-forming range was obtained. The glass transition temperatures increase with the GeO 2 concentration in the glasses. The vibrational modes of both bridging (Ge–S–Ge) and non-bridging (Ge–S − ) sulfurs are observed in Raman and IR spectra of binary Li 2 S + GeS 2 glasses. Additions of GeO 2 to this binary glass increase the bridging oxygen band (Ge–O–Ge) at the expense of decreasing the bridging sulfur band (Ge–S–Ge), whereas the bands associated with the non-bridging sulfurs (Ge–S − ) remain constant in intensity up to high GeO 2 concentrations. At higher concentrations of GeO 2 (⩾60%), the non-bridging oxygen band, which is not observed at low and intermediate GeO 2 concentrations, appears and grows stronger. From these observations, it is suggested that the added lithium ions favor the non-bridging sulfur sites over the oxygen sites to form non-bridging sulfurs, whereas the added oxygen prefers the higher field strength Ge 4+ cation to form bridging Ge–O–Ge bonds. The structural groups in the Li 2 S + GeS 2 + GeO 2 glasses that are consistent with results of Raman and IR spectra are described and are used to develop a structural model of these glasses.