Relationship Between Oxide-Ion Conductivity and Ordering of Oxygen Vacancy in the Ln₂Zr₂O₇ (Ln = La, Nd, Eu) System Using High Temperature XRD

The pyrochlore-type Ln₂Zr₂O₇ (Ln = La, Nd, Eu) systems were refined by Rietveld analyses of XRD data combined with the MEM-based pattern fitting at RT, 873, 1073, and 1273 K. All the samples kept a single cubic phase of the pyrochlore-type structure in the temperature range up to 1273 K. The oxide-ion conductivities of the present systems were discussed on a basis of ordering of oxygen vacancy in the pyrochlore-type structure. Theoxide-ion conduction of Eu₂Zr₂O₇ was ascribed to diffusion of oxygen along the $〈100〉$ direction, while the hole conduction of La₂Zr₂O₇ occurred along the $〈110〉$ direction, according to the charge density map estimated by the MEM analysis.