Inhomogenous broadening, charge compensation, and luminescence quenching in Ce³⁺-doped Sr₃AlO₄F phosphors

The local coordination around luminescent ions in phosphors can affect the properties of these materials. In this report, we analyze the Ce³⁺ luminescence for the various Ce³⁺ centers in Sr₃AlO₄F-based phosphors and use the excitation, emission, and quenching of these phosphors to infer aspects of the local coordination. It is shown that Ce³⁺ centers with lower energy 4f1→5d1 absorption bands are likely from charge compensation effects by the replacement of F- by O2-. In addition, at higher RE³⁺ concentrations, additional Ce³⁺ centers with even lower energy 4f1→5d1 absorption bands are present, presumably due to Ce³⁺-RE³⁺ pair formation and O2- charge compensation. These Ce³⁺ centers with lower energy 4f1→5d1 absorption bands have their luminescence strongly quenched at room temperature. The relationships between composition and Ce³⁺ luminescence quenching for Sr₃AlO₄F-based phosphors are also discussed, giving evidence that Ce³⁺(5d1) ionization is the main cause for luminescence quenching in these materials.