Positron annihilation study of vacancy-type defects in fast-neutron-irradiated MgO·nAl2O3

• Detection of Al monovacancy by positron lifetime spectroscopy in fast neutron-irradiated MgO·nAl2O3(n=2)MgO·nAl2O3(n=2).
• Concentration of defects is also estimated for Al monovacancy.
• O atom peak was observed by using coincidence Doppler broadening spectroscopy.

The positron lifetimes of fast-neutron-irradiated MgO·nAl2O3 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  × 10−3 m0c was observed, which may be due to the presence of oxygen atoms in the neighborhood of the vacancies.