Structure and ionic conductivity in doped LaGaO3

LaGaO3 doped with lower valence cations to create vacancies in the oxygen lattice is a promising new material for technical applications due to its excellent oxygen-ionic conductivity. In order to understand the conduction mechanism and its temperature dependence, neutron powder data were collected between 2 and 1273 K on the instrument E9 at HMI (Berlin). The structures were refined in space group I2/a derived from the ideal perovskite structure by anti-phase rotations of the O-6 octahedra around [100] and [011]. Strong anomalies of various parameters can be related to anomalies in the conductivity curve. Although the distortions are small and no corresponding splitting of the reflections is directly observable in the powder pattern, the profile refinement technique allows a reliable determination even of the monoclinic cell. Disorder effects are derived from an analysis of the atomic displacement parameters.