Diffusion Path of Oxide Ions in a Fast-ion Conductor La_0.64(Ti_0.92Nb_0.08)O₃ with a Double Perovskite-type Structure

Abstract

Densities of coherent-scattering lengths in A-site deficient double perovskite-type oxide La_0.64(Ti_0.92Nb_0.08)O₃ (P4/mmm) have been determined by a whole-pattern fitting approach based on the maximum-entropy method from neutron powder diffraction data measured at 496 degC, 1008 degC and 1358 degC. Oxide ions at the 4i site are largely distributed along the [101] directions near the stable position. These oxide ions migrate to nearest-neighbor 4i sites along the [100] and [010] directions near the (004) planes at 1008 degC and 1358 degC. The two-dimensionality of diffusion paths is attributable to the layered structure of the double perovskite-type La_0.64(Ti_0.92Nb_0.08)O₃ compound.