Elucidation of annihilation processes of defects induced by γ-irradiation in Li2TiO3

Annihilation behaviors of irradiation defects induced by γ-ray in Li2TiO3 were studied by means of ESR and compared to those by thermal neutron. The ESR spectra indicated that E′- and O−-centers were formed after the γ-ray irradiation and isochronal annealing experiments showed that the amounts of E′- and O−-centers, which are Frenkel pair, decreased in the temperature range of 550–650 K for the γ-ray irradiated sample, while for the thermal neutron irradiated one, those decreased in the lower temperature range of 400–500 K. The activation energies of recombination reaction of E′-center and O−-center were 0.68 ± 0.01 and 0.31 ± 0.04 eV for the γ-ray and the thermal neutron irradiated samples, respectively. In the γ-ray irradiated sample, the formation of defects is resulted from electron-excitations but that in thermal neutron irradiated one is mainly resulted from collision of energetic particles. Comparing with the γ-ray irradiated sample, it was found for the thermal neutron irradiated sample that O2−-center would be easily formed and the recombination process of E′- and O2−-centers would also take place. The processes of different defect formations like electron-excitation and collision processes, would produce the different defects such as O−- and O2−-centers, leading to the different annihilation behaviors of irradiation defects.