SYNCHROTRON RADIATION TI-K XANES STUDY OF TIO2-Y2O3-STABILIZED TETRAGONAL ZIRCONIA POLYCRYSTALS

Valence state and site symmetry of Ti ions in TiO2-Y2O3-ZrO2 powders with 2 mol% Y2O3 and 5, 10, 15, and 20 mol% TiO2, respectively, are studied by X-ray absorption near-edge spectroscopy (XANES). Tetravalent Zr4+ ions are replaced predominantly by Ti4+ ions. Within the solubility region of Ti ions, a subsequent displacement of Ti ions from the center of symmetry is observed with increasing TiO2 content in TiO2-Y2O3-stabilized tetragonal ZrO2 polycrystals (Ti-Y-TZP) under investigation. This behavior cannot be interpreted with a random substitution of Ti4+ ions on Zr4+ lattice sites. On the contrary, this correlation between the TiO2 content in Ti-Y-TZP and the shift of Ti ions indicates an increasing interaction between the Ti ions with growing TiO2 content, caused by a subsequent clustering of Ti ions.