A COMPARISON BETWEEN THE IRRADIATION DAMAGE RESPONSE OF SPINEL AND ZIRCONIA DUE TO XE ION-BOMBARDMENT

The mechanical properties of Xe-implanted spinel and cubic zirconia su rfaces, as determined by nano-indentation measurements, are distinct a nd the differences can be related to their microstructures. Upon Xe2ion irradiation to high dose at cryogenic temperature (120 K), the You ng's modulus of irradiated spinel falls dramatically until the modulus is only about 3/4 the un-irradiated value. The maximum modulus occurs concurrent with the formation of a metastable crystalline phase of sp inel. The subsequent elastic softening at higher Xe2+ doses is an indi cation of the onset of amorphization of the spinel. Xe-implanted zirco nia surfaces behave differently, in all cases showing almost no change in elastic modulus with increasing Xe2+ ion dose. This is consistent with microstructural observations of Xe-implanted zirconia crystals wh ich, unlike spinel, show no change in crystal structure with increasin g ion dose. The hardness of both spinel and zirconia increases slightl y for low Xe2+ ion doses. At higher doses, zirconia shows little chang e in hardness, while the hardness of the implanted spinel falls by mor e than a factor of two. The initial increase in hardness of both spine l and zirconia is consistent with point defect accumulation and the pr ecipitation of small interstitial clusters, while the drop in hardness of spinel at high Xe2+ ion doses is due to the formation of an amorph ous phase. (C) 1998 Elsevier Science S.A. All rights reserved.