Electronic structure, photoluminescence and phosphorescence properties in BaSc2Si3O10:Eu2+, RE3+ (RE3+ = Nd3+, Tm3+, Dy3+ and Tb3+) phosphors

Novel long lasting phosphorescence materials BaSc2Si3O10:Eu2+, RE3+ (RE3+ = Nd3+, Tm3+, Dy3+ and Tb3+) are designed and prepared by a solid state reaction. According to the density functional theory calculations, the conduction band is mostly composed of Sc 3d states, and Ba states have almost no contribution to the conduction band. Their photoluminescence emission spectra show a broad asymmetric blue emitting band peaking at about 443 nm, attributed to the 5d-4f transitions of Eu2+ ion occupying Ba and Sc site respectively. According to the analysis on electronic structure and optical properties of the phosphors, it is believed that due to the special form of conduction band and the occupying situation of emission center, only the Eu2+ ion occupying the Sc site is involved in the long lasting phosphorescence process, resulting in the interesting phenomenon that the blue emitting phosphors show green phosphorescence. Additionally, the experimental results show that co-doping the trivalent rare earth ions, especially Nd3+ or Dy3+ ions, can improve the long lasting phosphorescence performance effectively in BaSc2Si3O10:Eu2+ system. This work shows up an interesting phosphorescence phenomenon, and provides a direct experimental evidence that conduction band plays an important role in the long lasting phosphorescence process.