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.

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