Internal distortion in ZrO₂-CeO₂ solid solutions: Neutron and high-resolution synchrotron x-ray diffraction study

Neutron and high-resolution synchrotron x-ray diffraction measurements have indicated a tetragonal zirconia phase with both an axial ratio of unity and internal shear deformation: The oxygen displacements from ideal fluorite positions of 0.088 and 0.078 Å are observed for 65 and 70 mol% CeO₂-ZrO₂ samples, respectively, although both c/a values are 1.000±0.001. The c/a ratio decreases with increasing of CeO₂ content and decreases discontinuously to unity around a 60 mol% CeO₂ composition, while the oxygen displacement decreases continuously up to about 90 mol% CeO₂.