X-ray-absorption studies of zirconia polymorphs. III. Static distortion and thermal distortion.

Abstract

Static and dynamic Debye-Waller factors for the Zr(Y)-O shell and the Zr(Y)-Zr(Y) shell have been determined for four zirconia polymorphs from 10 K to room temperature. The apparent Einstein frequencies for cation-O vibrations and the Debye frequencies for cation-cation vibrations have also been obtained from the analysis. The higher phase stability and the stabilizing effect of Y dopants are manifest in the higher apparent vibrational frequencies. For tetragonal zirconia these frequencies correlate well with Raman data, and for cubic zirconia the Y-O frequency coincides with the unique Raman frequency for fluorite-structure oxides. Similar bonding in monoclinic and cubic zirconia yields similar vibrational frequencies, while a larger bond distance generally leads to a lower frequency. Comparison of the Debye-Waller factors obtained from extended x-ray-absorption fine structure and from neutron diffraction has also revealed the different extent of atom-atom correlation in atomic thermal motion for different bonding.