Radiation damage in neutron-irradiated yttria-stabilized-zirconia single crystals

Optical absorption measurements and luminescence experiments have been made in neutron-irradiated or thermochemically reduced yttria-stabilized-zirconia (YSZ) crystals. Two absorption bands centered at about 375 and 470 nm were observed after irradiation or reduction; however, the thermal stability of these bands in each case is very different. In irradiated crystals the bands disappear with heat treatments at ∼600 K, whereas in reduced crystals they anneal out at ∼1300 K. This difference is probably due to interstitial-vacancy recombination in the oxygen sublattice of the former crystals. Nano-indentation tests show that hardness and the elastic modulus remain practically unchanged after TCR or neutron-irradiation. These results confirm that YSZ single crystals are radiation resistant and that the radiation damage can be easily removed by anneals in air at temperatures above 600 K