Influence of ion irradiations on the microstructure in the tritium breeder material Li2TiO3

Tritium breeder materials are significant for the blanket design of a fusion reactor. Because of its good chemical stability and available tritium release behavior, Li2TiO3 has been selected as one of leading candidates for ceramic breeder materials. During a blanket operation, defects are introduced into tritium breeder materials by high energy neutrons and energetic particles from nuclear reactions, resulting in performance degration of the materials. He and O ion irradiation were applied to introduce irradiation damage into Li2TiO3 in this study. X-ray Diffraction (XRD) and Raman spectra experiments were performed to identify the evolution of the Li2TiO3 microstructure. The experimental results show that the atomic arrangement in Li2TiO3 is strongly disordered by the ion irradiation. The destruction of long-range order is confirmed by the reduction in XRD intensities. The destruction of short-range order is validated by the reduction in the Raman intensities and disappearance of Raman bands with increasing irradiation dose. The disorder in Li2TiO3 structure is considered to be associated with the species and energy of the ions. In order to further clarify the defects induced by ion irradiation, Electron Spin Resonance (ESR) was employed. E-centers which are oxygen vacancies occupied by one electron have been formed by ion irradiation. Compared with He ion irradiation, O ion irradiation produces relatively less E-centers, but more Ti3+ defects. These different defects induced by irradiation are discussed in relation to the disorder of microstructure.