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Abstract
We have studied the effect of yttria content on the recovery of paramagnetic centres in electron- and ion-irradiated yttria-stabilized zirconia (ZrO2: Y3+). Single crystals with 9.5 or 18 mol% Y2O3 were irradiated with 1.0–2.5 MeV electrons, 145-MeV carbon ions, 200-MeV iodine ions, 1.45-GeV xenon ions and 2.25-GeV gold ions at various fluences. Thermal annealing of electron (F+-type and T) centres and hole centres was studied by X-band electron paramagnetic resonance spectroscopy. Hole centres are found to anneal more quickly for 18 mol% than for 9.5 mol% Y2O3. At long annealing times, a non-zero asymptotic behaviour is observed in the isothermal annealing curves of hole centres and F+-type centres between 300 and 500 K. For the electron-irradiated samples, the asymptotic concentration of both defect types normalized by the values prior to annealing has a maximum value of ~0.5 for annealing temperatures below the onset of the (isochronal) recovery stage (400 K), regardless of the yttria content. For the ion-irradiated samples, larger normalized asymptotic values (~0.8) at high annealing temperature are found for the F+-type centres with a similar recovery process. Such an uncommon behaviour is analysed on the basis of a model using equilibrated reactions between point defects with different charge states.
Acknowledgements
Authors are indebted to the late Prof. A.M. Stoneham (University College London, UK) for fruitful discussions and advice. One of the authors (W.J. Weber) was supported by the US Department of Energy, Basic Energy Sciences, Materials Science and Engineering Division. C. Trautmann (Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany) and M. Toulemonde (CIMAP, Caen, France) are warmly thanked for the irradiations at GSI/UNILAC and GANIL.