Optical properties and energy transfer of a novel KSrSc2(PO4)3:Ce3+/Eu2+/Tb3+ phosphor for white light emitting diodes

A new langbeinite-type phosphate KSrSc2(PO4)3 has been synthesized by conventional high temperature solid state reaction. Rietveld structure refinement, a field emission scanning electron microscope, photoluminescence spectra, quantum efficiency as well as lifetimes were used to characterize the samples. Structure refinement reveals that KSrSc2(PO4)3 has two kinds of Sr2+ and Sc3+ sites for the doped ions to occupy, forming emission centers. The KSrSc2(PO4)3:Ce3+ and KSrSc2(PO4)3:Eu2+ phosphors both have broad excitation and emission bands due to spin- and orbit-allowed electron transitions. Phosphors with tunable blue to blue-green colors were obtained by codoping the Tb3+ ions into the KSrSc2(PO4)3:0.03Ce3+ and KSrSc2(PO4)3:0.03Eu2+ phosphors with varying contents. The mechanism of Eu2+→Tb3+ energy transfer is determined to be a dipole–quadrupole interaction in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors by using the Inokuti–Hirayama theoretical model. Our prepared KSrSc2(PO4)3:Ce3+,Tb3+ and KSrSc2(PO4)3:Eu2+,Tb3+ phosphors are of potential value for UV excited WLEDs.