Void Evolution in α-Al₂O₃ Irradiated by E_n ≥1 MeV Neutrons of 3 x 10²⁰cm^-2

The void evolution in α-Al₂O₃ irradiated by E_n ≥1 MeV neutrons of 3 x 10²⁰cm^-2 and post-annealed from 100°C to 1050°C has been studied by a positron annihilation lifetime technique. The void nucleation starts at 500°C. In the annealing temperature region from 550°C to 750°C, the radius of created voids keeps constant at a value of about 0.29 nm and the number of voids increases with increasing temperature. Afterwards,the radius of voids increases rapidly with the increasing annealing temperature and reaches 1.21nm at 1050°C.