Defect studies of a ZrO2 + 9mol%Y2O3 single crystal were performed in this work using a high resolution positron lifetime spectroscopy combined with slow positron implantation spectroscopy. In order to elucidate the nature of positron trapping sites observed experimentally, the structural relaxations of several types of vacancy-like defects in zirconia were performed and positron characteristics for them were calculated. Relaxed atomic configurations of studied defects were obtained by means of ab initio pseudopotential method within the super-cell approach. Theoretical calculations indicated that neither oxygen vacancies nor their neutral complexes with substitute yttrium atoms were capable of positron trapping. On the other hand, zirconium vacancies were deep positron traps and were most probably responsible for the saturated positron trapping observed in yttria stabilized zirconia single crystals. However, the calculated positron lifetime for zirconium vacancy was apparently longer than the experimental value corresponding to a single-component spectrum measured for the cubic ZrO2 + 9 mol. % Y2O3 single crystal. It was demonstrated that this effect could be explained by hydrogen trapped in zirconium vacancies. On the basis of structure relaxations, it was found that zirconium vacancy – hydrogen complexes represent deep positron traps with the calculated lifetime close to the experimental one. In zirconium vacancy – hydrogen complexes the hydrogen atom forms an O-H bond with one of the nearest neighbour oxygen atoms. The calculated bond length was close to 1 Å.

Investigation of Hydrogen Interaction with Defects in Zirconia. O.Melikhova, J.Kuriplach, J.Čížek, I.Procházka, G.Brauer, W.Anwand: Journal of Physics - Conference Series, 2010, 225[1], 012035