Radiation damage effects in zirconia

The evolution of radiation-induced damage in fully-stabilized, cubic zirconia (FSZ) (Y, Ca and Er dopants acting as stabilizers) and in pure, unstabilized, monoclinic zirconia, was investigated using Rutherford backscattering spectrometry and ion channeling (RBS/C), along with X-ray diffraction and transmission electron microscopy (TEM). FSZ crystals were irradiated with 340-400 keV Xe++ ions and at temperatures ranging from 170 to 300 K, or with I-127(+) ions (72 MeV) at temperatures ranging from 300 to 1170 K. No amorphization of zirconia was found under any irradiation condition, though in the case of 72 MeV I+ ion irradiations, the irradiation-induced defect microstructure was observed to produce dechanneling effects in RBS/C measurements that reach the 'random' level. Damage accumulation in Xe-ion irradiation experiments on FSZ crystals was found to progress in three stages: (1) formation of isolated defect clusters; (2) a transition stage in which damage increases rapidly over a small range of ion dose, due to the linking of dislocations and defect clusters: and (3) a 'saturation' stage in which damage accumulation is retarded or increases only slowly with ion dose. The FSZ crystal composition does not seem to alter significantly the dose-dependence of these damage stages. Unstabilized, monoclinic ZrO2 was observed to transform to a higher symmetry, tetragonal or cubic phase, upon 340 keV Xe++ ion irradiation to Xe fluences in excess of 5 x 10(18) m(-2) (dose equivalent, similar to 2 displacements per atom or dpa) at 120 K. This transformation was accompanied by a densification of the ZrO2 phase by similar to 5%. No amorphization of the pure ZrO2 was observed to a Xe++ ion fluence equivalent to a peak displacement damage level of about 680 dpa. (C) 1999 Elsevier Science B.V. All rights reserved.