Abstract
We report the results of a neutron powder diffraction study of the yttrium tantalates Y0.785Ta0.215O1.715 and Y0.7Ta0.3O1.8. In the orthorhombic fluorite-related Y0.7Ta0.3O1.8 compound, the Y and Ta atoms were occupationally ordered, and the oxygen ions were localized at around the stable positions. On the contrary, in the defect fluorite-type cubic Y0.785Ta0.215O1.715 material, the Y and Ta atoms were occupationally disordered, and the oxygen ions exhibited a large spatial distribution and positional disorder. At a higher temperature of 808 K, the spatial distribution of the oxygen ions was larger, and the diffusion paths of the oxygen ions were observed along the 〈100〉 directions. The high diffusion coefficient and conductivity of oxygen ions in cubic Y0.8Ta0.2O1.7 are attributable to the occupational and positional disorder.
Published Version
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