Local structures surrounding Zr in nanostructurally stabilized cubic zirconia: Structural origin of phase stability.

Local environment surrounding Zr atoms in the thin films of nanocrystalline zirconia (ZrO₂) has been investigated by using the extended x-ray absorption fine structure (EXAFS) technique. These films prepared by the ion beam assisted deposition exhibit long-range structural order of cubic phase and high hardness at room temperature without chemical stabilizers. The local structure around Zr probed by EXAFS indicates a cubic Zr sublattice with O atoms located on the nearest tetragonal sites with respect to the Zr central atoms, as well as highly disordered locations. Similar Zr local structure was also found in a ZrO₂ nanocrystal sample prepared by a sol-gel method. Variations in local structures due to thermal annealing were observed and analyzed. Most importantly, our x-ray results provide direct experimental evidence for the existence of oxygen vacancies arising from local disorder and distortion of the oxygen sublattice in nanocrystalline ZrO₂. These oxygen vacancies are regarded as the essential stabilizing factor for the nanostructurally stabilized cubic zirconia. [ABSTRACT FROM AUTHOR]