Effect of Oxygen Vacancies on the Persistent Luminescence of Y3Al2Ga3O12:Ce3+,Yb3+ Phosphors.

The effect of oxygen vacancies (VO) and the atmosphere influence on persistent luminescence (PersL) in Y3Al2Ga3O12 (YAGG):Ce3+,Yb3+ are investigated by heating it in CO2, air, and 10% H2/90% Ar atmospheres. The VO-rich YAGG phosphors with outstanding PersL are successfully obtained by the common contribution of the reducing atmosphere and the incorporated Yb3+ ions, and the concentration of oxygen vacancies in the phosphors is characterized by X-ray photoelectron spectroscopy and electron paramagnetic resonance measurements. Compared to the best sample prepared in neutral CO2, the reduced sample shows an increase of 30% in initial intensity and 100% in duration time, while the oxidized sample decreases drastically and shows a faint and undetectable PersL. The enhancement is mainly caused by the abundant formation of VO, which is achieved by the pairing of VO with Yb2+ ions. The newly created VO by the reducing calcination is inferred to be adjacent to the Yb site and forms a compensation-type defect cluster due to the charge compensation effect. These findings reveal that understanding the effect and formation of VO is of great significance to design a high-performance phosphor.