MICROSCOPIC STRUCTURE OF THE GLASSY IONIC CONDUCTOR X-CENTER-DOT-LIF-X)CENTER-DOT-LIPO3 FROM NMR DATA((1)

The structure of phosphate glasses of the nominal composition x . LiF + (1 - x) . LiPO3 has been studied for 0 < x < 0.35, using H-1, Li-7, F-19, P-31 NMR. By combining data from different nuclei and various so lid state NMR techniques structural information on the molecular scale is obtained. The measurements confirm that the structural units of th e glass are polyphosphate chains, and allow determination of their ave rage length. The increase of LiF concentration, x, from 0 to 0.35 lead s to a shortening of the chains from 29 to 4 phosphate units by use of Li and F to form terminal groups. Fluorine is partitioned between two structural units: fluorophosphate terminal groups and Li+F- fragments , in a ratio of about 1:1 at low x and decreasing to 1:4 at high x. Su bstantial loss of fluorine during glass preparation is observed and me asured. (C) 1998 Elsevier Science B.V. All rights reserved.