High-resolution electron energy loss spectroscopy spectra were obtained for several members of the vacancy-doped metal/insulator perovskite system Nd1−xTiO3 where NdTiO3 (x = 0) was a Mott–Hubbard insulator and Nd2/3TiO3 (x = 0.33), a band insulator. The insulator to correlated-metal transitions occur at x ≈ 0.20 and x ≈ 0.10. Both OK- and Ti L2,3-edge data were obtained on the title materials and the related d0 perovskites, CaTiO3, SrTiO3 and BaTiO3. The crystal structure of Nd0.70TiO3 (x = 0.30) was refined from powder neutron data in Cmmm which was taken as a model for the structure of Nd2/3TiO3 (x = 0.33) as well. The L-edge spectra for Nd1−xTiO3 exhibited systematic changes consistent with the valence state evolution from all Ti3+ (x = 0.0) to all Ti4+ (x = 0.33). Octahedral crystal fields of 1.5 and 2.0eV were inferred from the L-edge data for NdTiO3 and Nd2/3TiO3 by comparison with calculated spectra from the literature. Broader L3 and L2 peak widths for Nd2/3TiO3 than for the other d0 perovskites were attributed to the more complex crystal structure of this material which includes two Nd sites with partial occupation and a more distorted Ti–O environment with low site symmetry. A markedly different OK-edge spectrum for Nd2/3TiO3 was attributed to the involvement of Nd 5d levels.

High-Resolution EELS Study of the Vacancy-Doped Metal/Insulator System, Nd1-xTiO3, x = 0 to 0.33. A.S.Sefat, G.Amow, M.Y.Wu, G.A.Botton, J.E.Greedan: Journal of Solid State Chemistry, 2005, 178[4], 1008-16