X-RAY-ABSORPTION STUDIES OF ZIRCONIA POLYMORPHS .2. EFFECT OF Y2O3 DOPANT ON ZRO2 STRUCTURE

Extended x-ray-absorption fine structure and x-ray-absorption near-edge structure spectra at both the Zr and Y K edge have been obtained at 10 K and room temperature for solid ZrO2-Y2O3 solutions. Zr has very different local structures in the tetragonal and cubic solid solutions in terms of the oxygen-bond distances and coordination number. In contrast, the Y local structure is nearly the same in all of the solid solutions. Charge-compensating oxygen vacancies caused by Y doping are preferentially located next to Zr ions, leaving eightfold oxygen coordination for the Y ions. The nearest-neighbor and next-nearest-neighbor distances in these solid solutions do not follow the virtual-crystal approximation with reference to x-ray-diffraction lattice parameter. The distortion of the Zr-cation shell in cubic solid solutions is especially severe so that the long-range fluoritelike order implied by global cubic symmetry is not manifested in the local atomic environment.