Color-tunable properties based on complex anion substitution in Eu2+ doped Ca8Sc2(PO4)6-y(SiO4)1+y phosphor

We synthesized and investigated the effect of Eu2+ ions doping in a novel phosphor-silicate Ca8Sc2(PO4)6(SiO4) phosphor. The structure and photoluminescence properties were determined by X-ray powder diffraction Rietveld refinement, diffuse reflection spectra, emission-excitation spectra, decay curves and temperature dependence spectra. The phosphors showed an asymmetric broad-band blue emission (Eu2+) with peak at 470 nm. Furthermore, we presented the Ca7.96Sc2(PO4)6-y(SiO4)1+y:0.04Eu2+ phosphors by co-substituting [Eu2+-Si4+] for [Ca2+-P5+], and different behaviors of luminescence evolution in response to structural variation were verified among the series of phosphors. The results were attributed to the presence of multi Ca2+ sites, resulting in the mixing of blue and green emissions for Eu2+ ions. The complex anion substitution of [PO4]3- by [SiO4]4- induced an increased crystal field splitting of the Eu2+ ions, which caused a decrease in emission energy from the 5d excited state to the 4f ground state and a resultant red-shift from 470 nm to 520 nm. All the properties indicated that the Ca8Sc2(PO4)6(SiO4):Eu2+ phosphors have potential application for color-tunable WLEDs.