Tsuyoshi Okamoto

The transformation behavior induced by water for Y-TZP containing transition metal oxides.

In order to study the influence of transition elements present in grain boundary on the stress corrosion of zirconia, yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) containing transition metal oxides such as CoO, FeO and NiO were chosen and annealed in air or soaked in water. The relations of the amount of monoclinic ZrO2 formed by annealing or soaking against the annealing or soaking time were obtained in each sample. The results were summarized in the following.(1) The doped transition elements were present primarily in grain boundaries of specimens. The amount of monoclinic ZrO2 formed by annealing or water-soaking decreased with an addition of the transition elements.(2) The transformation rate was proportional to the concentration of tetragonal ZrO2 on the surface. This indicated that the transformation induced by annealing or water-soaking was caused by the stress corrosion by water.(3) In the early stage of soaking in water the transformation rate of species containing transition elements greatly changed itself, which could be explained by the stress corrosion mechanism.