X-RAY PHOTOELECTRON-SPECTROSCOPY INVESTIGATION ON THE LOW-TEMPERATUREDEGRADATION OF 2 MOL-PERCENT Y2O3-ZRO2 CERAMICS

2 mol% Y2O3-ZrO2 polycrystals were annealed in water and under vacuum to highlight the effect of the presence of H2O on the low-temperature degradation transformation. The specimen surfaces with monoclinic phas es transformed during annealing in the different environments were ana lyzed by X-ray photoelectron spectroscopy with special interest on the electron binding energy change of the constituent ions of the 2 mol% Y2O3-ZrO2 ceramics after the degradation transformation, It was found that no change occurred for the electron-bonding energies of core leve ls of zirconium ions after the transformation, whereas Y-OH bonds were formed during annealing in water. This result suggested a possibility that the preferred hydration of yttrium took place at the surface of Y2O3-partially-stabilized ZrO2, which is likely to be the reason for t he low-temperature degradation accelerated by the presence of H2O.