In Situ Neutron Diffraction Study on Fast Oxide Ion Conductor LaGaO₃-Based Perovskite Compounds

Abstract

The crystal structures of LaGaO3, LaGa0.9Mg0.1O2.95, and La0.9Sr0.1Ga0.9Mg0.1O2.9 have been investigated by high-temperature neutron powder diffraction in order to clarify a mechanism for high oxide ion conduction properties in LaGaO3-based compounds. Parent phase LaGaO3 crystallized in the orthorhombic (Pbnm) up to 150 °C and the rhombohedral (R3̄c) at between 160 and 800 °C. LaGa0.9Mg0.1O2.95 crystallized in the orthorhombic (Ibmm) up to 340 °C and the rhombohedral (R3̄c) at between 350 and 800 °C. On the other hand, La0.9Sr0.1Ga0.9Mg0.1O2.9 crystallized in the monoclinic (I2/a) up to 400 °C and the rhombohedral (R3̄c) at between 410 and 800 °C. The correlations between the crystal structures and conduction properties of LaGaO3-based materials were discussed on the basis of the analytical results.