A structural study of Li₂S B₂S₃ glasses by neutron diffraction

Abstract

The radial distribution functions (RDFs) of five xLi₂S.(1-x)B₂S₃ glasses (x = 0.55, 0.60, 0.67, 0.71 and 0.75) have been determined from neutron diffraction experiments performed at the Institut Laue-Langevin, Grenoble. These glasses are prepared by casting a molten mixture of boron, sulphur and Li₂S inside a controlled atmosphere glovebox. Addition of the Li₂S modifier is found gradually to suppress all peaks corresponding to interatomic distances > 3.5 Å, which implies that the structural entities present in these glasses become segmented, and therefore more ionic, as x increases. The assumption of the existence of four main structural entities based on four- and three-coordinated borons (the latter carrying bridging and/or non-bridging sulphurs) accounts for all the peaks present in the RDFs as a function of composition. Furthermore, in the most modified glass (x = 0.75), that which contains only 'isolated' BS^3-₃ triangles, there seems to be evidence for either octahedral or tetrahedral coordination of Li⁺ by S^- ions.