Radiation damage in zirconia investigated by positively charged particles

Abstract

Positrons, positive muons and deuterons were used – when applicable – to probe the production and thermal stability of defects induced at room temperature either by electron irradiation or He-ion implantation in zirconia stabilized by yttria in the cubic phase. No change in the positron lifetime or in the muon spin relaxation occurs after electron irradiation, indicating a positron saturation trapping in the annealed state, owing to the presence of structural defects inherent to phase stabilization. In contrast, after helium implantation, even at low fluence (∼1014cm−2), slow positron implantation spectroscopy reveals the presence of a new type of defect (being more trapping effective than the native ones), whereas neither positronium nor muonium are detected. The diffusion of helium was followed after 3He-ion implantation and subsequent annealing using the 3He(d,p)4He nuclear reaction. A two-Gaussian distribution fit indicates that a part of the helium atoms is trapped at the projection range location, most likely in gas bubbles, while the other part diffuses and out-gasses after heat treatment already at around 1/5 of the melting temperature. In spite of differences in depths and concentrations probed by the present techniques, a fairly good correlation is observed between the various results.