Relationship Between Oxide-Ion Conductivity and Ordering of Oxygen Vacancy in the Ln2 Zr2 O7 (Ln = La, Nd, Eu) System Using High Temperature XRD

Abstract

The pyrochlore-type Ln2 Zr2 O7 (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 Eu2 Zr2 O7 was ascribed to diffusion of oxygen along the 〈100〉 direction, while the hole conduction of La2 Zr2 O7 occurred along the 〈110〉 direction, according to the charge density map estimated by the MEM analysis.