Titanium local environment and electrical conductivity of TiO2-doped stabilized tetragonal zirconia

Solid state reactions in the ZrO2-Y2O3-TiO(2)system have been studied and the solid solubility limit of TiO2 in yttria stabilized tetragonal zirconia Y-TZP has been stablished. Structural characterization was carried out by XRD studies, and the changes in local structures with increasing TiO2 in yttria stabilized tetragonal zirconia was analyzed for the first time by EXAFS and XANES measurements. The XANES results indicate a displacement of Ti ions from the center of symmetry with increasing titania content leading to assume a non randomly substitution of Ti4+ on Zr4+ sites in the tetragonal zirconia lattice. From the Ti-O and Ti-Ti measured distances, it has been assumed that the found electrical conductivity decrease with increasing titania content was due to both a trapping of the oxygen ion vacancies at Ti ions (Ti'(Zr) Vo) and the formation of more complex associations like (Ti'(Zr) Vo Ti'(Zr) Vo), which giving rise to a reduction in the global concentration of moving oxygen vacancies. (C) 2000 Kluwer Academic Publishers.