Mixed Glass Former Effect in the System 0.3Li₂S−0.7[(1−x)SiS₂−xGeS₂]: A Structural Explanation

A mixed glass former effect has been observed in the glassy system 0.3Li 2 S−0.7[(1− x )SiS 2 − x GeS 2 ], where 0 ≤ x ≤ 1. It corresponds to a large enhancement of ionic conductivity for compositions 0.50 ≤ x ≤ 0.64. The variations of the electrical characteristics are closely related to those of the glass transition temperature and the density. Structural investigations by Raman and SAXS techniques have been carried out on this system. The results indicate that the high conducting glasses belonging to the central composition region, i.e., 0.50 ≤ x ≤ 0.64, are phase separated, forming entities with a composition close to GeS 2 which are embedded in a matrix close to Li 2 SiS 3, while glasses from the limiting composition ranges, i.e., 0 ≤ x < 0.50 and 0.64 < x ≤ 1, are homogeneous.