Computational study of inferior persistent performance of La3GaGe5O16 phosphor

Using first-principles calculations, we investigate the atomic and electronic structure of La3GaGe5O16 and its oxygen vacancies with an aim to evaluate the potential of La3GaGe5O16 as a new persistent phosphor. We find that oxygen vacancies prefer the bridging sites within [GemOn] groups over the bridging sites between groups. Oxygen vacancies are found to act as an electron trap center and their trap states are of conduction band character of the host. By comparison with other excellent persistent phosphors, we suggest that La3GaGe5O16 cannot emerge as an efficient persistent phosphor, and the most likely cause is the formation of ring structure and rather localized conduction band of the host. The ring structure makes most of oxygen atoms structurally inactive and the localized conduction band results in low concentration of trapping electrons. Our results thus provide fundamental explanations for the inferior persistent performance of La3GaGe5O16 phosphor.