A study of Li2TiOSiO4 and Li2TiOGeO4 by X-ray powder and electron single-crystal diffraction, 17O MAS NMR and O K-edge and Ti L2,3-edge EELS

X-ray powder and electron single-crystal diffraction of crystals of Li(2)TiOSiO(4) and Li(2)TiOGeO(4) showed them to be tetragonal, space group P4/nmm unit-cell parameters a = 6.4379(2), c = 4.40032(2) Å for Li(2)TiOSiO(4) and a = 6.6110(8), c = 4.4372(6) Å for Li(2)TiGeO(4). The compounds are isostructural with their sodium analogues but are considerably compressed along the c axis owing to the smaller size of lithium compared with sodium atoms. Square-pyramidal TiO(5) groups are joined in these compounds by tetrahedral SiO(4) and GeO(4) groups, respectively. (17)O nuclear magnetic resonance spectra of the two compounds, isotopically enriched with (17)O, showed peaks due to the apical titanyl, Ti-O, and basal, bridging, Ti-O-Si or Ti-O-Ge, oxygen atoms of the title compounds. By comparison with reference spectra, oxygen K edges and titanium L(2,3) edges of electron energy-loss spectra were tentatively assigned.