Relation between Distortions in the Oxygen Sublattice and the Local Order of Zr in Nanostructured ZrO2–CeO2 Mixed Oxides

In the present work, the local order of Zr in ZrO2–CeO2 nanopowders (with 50, 65, 70, and 90 mol % CeO2) was studied by extended X-ray absorption fine structure around the Zr K-edge. In the cases of ZrO2–50 and 65 mol % CeO2, we studied how the local order is affected by the phase transition at high temperature. In order to study the tetragonal-cubic phase transition as a function of temperature, high-temperature synchrotron radiation X-ray powder diffraction (SR-XPD) was employed. We explored different models of the local atomic structure and interpreted them as distortions of the accepted long-range order deduced by XPD analyses. The results suggested the existence of distortions in the oxygen sublattice, which can be accounted for as displacements of the oxygen atoms along the (110) direction of the pseudofluorite unit cell that cannot be observed by XPD because of the random nature of these displacements.