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

The effect of oxygen vacancies (V_O) 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 V_O-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 V_O, which is achieved by the pairing of V_O with Yb²⁺ ions. The newly created V_O 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 V_O is of great significance to design a high-performance phosphor.