Irradiation effects on ion conductivity of lithium oxide

Lithium oxide (Li2O) as a solid breeder material for fusion reactors will be subjected to severe neutron irradiation. This paper reports the irradiation effects on the ion conductivity of Li2O during and after irradiation studied using oxygen ion (120 MeV) and lithium ion (24 MeV and 60 MeV) irradiation. From measurements at various temperatures, conductivity in the post-irradiation condition (irradiation-interrupted condition) was increased in the range 453 to 573 K by the F+ centers. The unspecified defects may be lithium-ion vacancies themselves or O-centers. The conductivity during irradiation was much larger than that in the irradiation-interrupted condition. The change in conductivity due to changing from the irradiation-interrupted condition to the during-irradiation condition increased with the ion flux. The differences were attributed not only to the temperature rise due to ion beam heating but also to the high concentration of fresh elementary irradiation defects and electrons and holes excited into the conducting state during irradiation. Irradiation effects on diffusion of lithium ions and tritium are discussed