CRYSTAL STRUCTURE OF Li_6-3xAl_xGe₂O₇ PREPARED VIA A SOL-GEL METHOD. H. S. W. Chang, J. C. Wang, K. Guo, L. S. Liou, C. M. Tsai, Department of Chemistry, Soochow University Taipei, Taiwan, 11102, ROC

A new phase of Li_6-3xAl_xGe₂O₇ (x ~ 0.1)has been synthesized via a sol-gel method. The compound has a Li₆Ge₂O₇ related monoclinic structure, but with double cell volume. A hexagonal tunnel formed honeycomb structure, along b-axis, was found in the lattice. It also shown every two of seven hexagonal tunnels contain lithium ions in the tunnels. The properties of the lithium ions, in the tunnels, are believed different from that of the lithium ions form the hexagonal frame work structure. The lithium ions, within the tunnels, are surrounded by two boat form twisted hexagonal layers. Each layer contain three oxygen atoms. The distance between the lithium ion and the six oxygen atoms, on two adjacent layers, are around (a) first layer: 1.992(27), 1.983(31), and 3.079(21) Å, and (b) second layer: 2.056(27), 2.153(26), and 3.487(27) Å. This shows the location of lithium ions in the tunnels are close to the wall of the tunnel. The honeycomb structure and the bonding of the lithium ions can very possibility make them mobile lithium ions. The lithium ions are expected to move in the tunnels and make the obtained Li_6-3xAl_xGe₂O₇ (x ~ 0.1) a possible new material for lithium ion conductor.

The structure of the compound was determined by single-crystal data and refined to R=0.0449 for 2252 reflections. The crystallographic data are; Monoclinic, P2₁/c, a=16.2430(10), b=5.400(10), c=15.8161(10) Å, [[club]]=118.490(0)^deg., and Z=8.