In order to obtain a better understanding of the oxide ion conductivity in perovskites, the structure of La0.9Sr0.1B0.9Mg0.1O3-δ, B = Al, Ga and Sc, were investigated by time-of-flight powder neutron diffraction at room temperature, 270, 470, 750, 850 and 950C. For all compounds, at all temperatures, structural and anisotropic thermal parameters were refined by full profile Rietveld methods to weighted profile R values less than 0.063. The changes in difference nuclear densities, due to changes in temperature, were illustrated by difference density maps around the atoms. The observed difference densities were described mainly by zeroth- and second-order spherical harmonics (quadrupolar functions), the nature of which vary with atomic site. The difference density maps provide a direct picture of the average in space and time of changes in atomic thermal vibrations. These observations were less biased by the least-squares method than refined parameters. The largest vibrational changes were found for the oxide ions. The magnitude of vibrational changes corresponds well with the magnitude of the conductivity. The oxide ion site in La0.9Sr0.1Ga0.9Mg0.1O3-δ had the highest vibrational change and the highest conductivity.

Correlation between Thermal Vibration and Conductivity in La0.9Sr0.1B0.9Mg0.1O3-δ, B = Al, Ga and Sc. D.Lybye, K.Nielsen: Solid State Ionics, 2004, 167[1-2], 55-63