Microstructure of Hardened and Softened Zirconia After Xenon Implantation

摘要

Ion channeling and transmission electron microscopy (TEM) techniques were used toexamine the microstructure of single-crystal Y2O3 stabilized cubic zirconia (YSZ) after implantation with 240 keV Xe+ ions. The observed microstructure was related to Knoop indentation hardness measurements. These measurements showed an increase in hardness for low ion-doses, reaching some maximum value, then a decrease in hardness at higher doses. In the hardening regime, below 7.5 x 10 15 Xe+ cm2, point defects and dislocation networks were observed by TEM. Ion-channeling showed a corresponding increase in damage as a function of ion-dose. For doses between 7.5 x 10 to the 15th power and 3 x 10 to the 16th power Xe+/cm2 the hardness falls, and the amount of damage, measured with ion-channeling, reaches a limiting value at less than complete damage. In this dose range the Xe concentration continues to increase beyond the dose where the amount of damage saturates. For high doses, greater than 3 x 10 to the 16th power Xe+/cm2, where softening of the zirconia occurs, additional reflections appear in the electron diffraction pattern that are consistent with the lattice parameter of solid Xe. A diffuse ring is also visible; this is believed to be due to the presence of fluid Xe. Both ion-channeling and TEM show that a significant amount of monocrystalline zirconia remains even up to doses of 1 x 10 to the 17th power.