Positron annihilation at planar defects in oxides

Planar defects may exhibit free volumes which, in principle, are detectable using positron annihilation spectroscopy. In this contribution, we present a preliminary theoretical study of positron trapping at stacking faults in zinc oxide and at a grain boundary in zirconia. In particular, we calculate the positron lifetime and positron binding energy to such defects. In the case of the grain boundary in zirconia, the influence of the yttrium segregation on the GB structure and positron characteristics is also examined. Calculated structural and positron characteristics are critically compared with experimental and other calculated data.