Electronic structure, photoluminescence and phosphorescence properties in Sr₂ScGaO₅:Sm³⁺

Novel reddish long lasting phosphorescence material Sr₂ScGaO₅:Sm³⁺ was designed and prepared by a solid state reaction. The results of morphology showed that the irregular microparticles were formed by the agglomeration of uniform submicron particles with the size of about 0.5–1 μm. The electronic structure with an indirect bandgap was evaluated in detail by the density functional theory calculations and the diffuse reflectance spectrum for the first time. By the two different methods, the bandgap energy of Sr₂ScGaO₅ was determined to be about 4.24 and 4.75 eV, respectively. The emission of Sm³⁺ ion at 604 nm is strongest in the photoluminescence process, while in the phosphorescence process the emission at 619 nm is dominant. According to the analysis on the optical properties, the interesting phenomenon about the difference between the photoluminescence and phosphorescence was revealed and explained by the fact that the conduction band played an important role in the phosphorescence process. Additionally, the result showed that the material can be stimulated effectively in very short time and would have great potential in the applications such as AC-light emitting diodes.