The structures of these fast-ion conducting glasses were studied by using neutron diffraction techniques and Monte Carlo simulations. It was found that the short-range structure of the B-O network was almost unchanged upon increasing the dopant salt concentration, and was independent of the nature of the dopant salt. On the other hand, the intermediate-range order of the B-O network decreased significantly with increasing dopant salt concentration. The Na borate glasses tended to be slightly more ordered than the corresponding Li borate glasses. The differences were attributed to the fact that the Li-borate glasses consisted of a disordered random mixture of many different types of borate configuration, while the Na borate glasses were built up of randomly distributed diborate groups, as suggested by previous nuclear magnetic resonance results. However, the Monte Carlo simulations of the most highly LiCl- and NaCl-doped glasses showed that large density fluctuations occurred within the B-O network. The voids were of widely differing sizes and geometries. The present results demonstrated that the intermediate-range order of the LiCl- and NaCl-doped glasses was significantly different to that reported for the analogous AgI-doped glasses. In the latter glasses, the B-O network formed a more ordered chain-like structure; with the salt ions cross-linking chains.

J.Swenson, L.Börjesson, W.S.Howells: Physical Review B, 1998, 57[21], 13514-26