Luminescence properties of Eu-activated alkaline and alkaline-earth silicate Na2Ca3Si6O16

Yellow-emitting phosphors of Na2Ca3Si6O16:Eu2+ was prepared by wet chemistry sol–gel method. X-ray powder diffraction and SEM measurements were applied to characterize the structure and morphology, respectively. The luminescence properties were investigated by the photoluminescence excitation and emission spectra, decay curve (lifetimes), CIE coordinates and the internal quantum efficiencies. The excitation spectra can match well with the emission light of near UV-LED chips (360–400 nm). Na2Ca3Si6O16:Eu2+ presents a symmetric emission band from 4f65d1 ⟶ 4f7(8S7/2) transitions of Eu2+ ions on doping below 3.0 mol%. On increasing Eu-doping levels, the sample contains two kinds of emission centers, i.e., Eu2+ and Eu3+ ions, which present the characteristic broad band (5d ⟶ 4f) and narrower (4f ⟶ 4f) luminescence lines, respectively. The energy transfer, the luminescence thermal stability (activation energy ΔE for thermal quenching) and luminescence mechanism of Na2Ca3Si6O16:Eu2+ phosphors were discussed by analyzing the relationship between the luminescence characteristics and the crystal structure.