Positron annihilation study of vacancy-type defects in fast-neutron-irradiated MgO center dot nAl(2)O(3)

The positron lifetimes of fast-neutron-irradiated MgO center dot nAl(2)O(3) single crystals were measured to investigate the formation of cation vacancies. Al monovacancy was possibly observed in samples irradiated by fast neutrons at ultra-low temperatures. Additionally, vacancy-oxygen complex centers were possibly observed in samples irradiated at higher temperatures and fast neutron fluences. Coincidence Doppler broadening (CDB) spectra were measured to obtain information regarding the vicinity of vacancy-type defects. A peak at approximately 11 x 10(-3) m(0)c was observed, which may be due to the presence of oxygen atoms in the neighborhood of the vacancies. (C) 2014 Elsevier B.V. All rights reserved.