Characterization of cation disorder and oxygen vacancies in Li‐rich Li 2 TiO 3

Li 2 TiO 3 has a broad stoichiometric range and wide application prospects such as cathode, tritium breeder, and microwave dielectric materials. Particularly, Li 2 TiO 3 shows a faster tritium release performance and exceptional chemical and radiation stabilities, making it one of the most promising solid breeder materials. Li‐rich Li 2 TiO 3 has been developed for years as an advanced breeder material due to its enhanced tritium production and better stability in hydrogen atmosphere. However, the defect chemistry responsible for accommodating excess Li and how the non‐stoichiometry improves the material's performance is still unclear. In this work, the crystal structure and non‐stoichiometry‐induced defects in Li‐rich Li 2 TiO 3 were investigated by means of X‐ray diffraction, electron spin resonance, and X‐ray photoelectron spectroscopy. Results show that oxygen vacancies and cation disorder both play a major role in the incorporation of excess Li. The sintering atmosphere (air/vacuum) has a negligible effect on the formation of the non‐stoichiometry‐induced defects but will influence the concentration of the oxygen vacancies. The better stability in the reduction atmosphere may be ascribed to the oxygen vacancies inside the Li‐rich Li 2 TiO 3 crystals.