Disorder and Diffusion Path of Oxide Ions in Ion Conductors

Abstract

We review our recent works on the positional disorder and diffusion path of oxide ions in Bi₂O₃, CeO₂ and (La_0.8Sr_0.2) (Ga_0.8Mg_0.15Co_0.05) O_3-δ. These were studied through the nuclear density distribution obtained by a combined technique including a Rietveld refinement, a maximumentropy method (MEM) and MEM-based pattern fitting of the neutron powder diffraction data measured at high temperatures. Oxide ions in fluorite-type structured δ-Bi₂O₃ and CeO₂ have a complicated disorder spreading over a wide area and shift to the ‹111› directions from the ideal fluorite site at higher temperatures. Diffusion path of oxide ions in (La_0.8Sr_0.2) (Ga_0.8Mg_0.15Co_0.05) O_3-δ perovskite is not along the straight line between the ideal positions, but exhibits an arc shape away from the B-site cation (Ga_0.8Mg_0.15Co_0.05) .