Synthesis And Luminescent Properties Of Rare-earth Ions-activated KNaCa₂（PO₄）₂Phosphors

Rare-earth ions doped phosphate phosphors were studied extensively for White lightemitting diodes (LEDs), because they have the advantages of good luminescent properties.Some kinds of KNaCa2(PO4)2phosphor doped with rare-earth ions Ce3+, Dy3+, Tb3+, Sm3+,and Eu2+were fabricated by high temperate solid-stated method. We studied their luminescentproperties and have a preliminary theoretical analysis:(1) Phosphors of KNaCa2(PO4)2:Ce3+,Dy3+were prepared by high temperature solid-statereaction. The luminescence properties of Ce3+and Dy3+ions, and the energy transferfrom Ce3+to Dy3+were investigated. The characteristic emission peaks of Ce3+(360nm)and Dy3+(481nm,574nm) exist simultaneously in the emission spectrum of phosphorswith considerable intensity under near-ultraviolet excitation (319nm). The investigativeresults indicate there an effective energy transfer from Ce3+to Dy3+in KNaCa2(PO4)2host. The varied emitted color of the phosphors from indigo to white can be achieved bytuning the relative ratio of Ce3+and Dy3+.(2) KNaCa2(PO4)2:Ce3+, Tb3+was synthesized by high temperature solid-state reaction andthe luminescence properties were also investigated. Fluorescence spectra measurementsindicated that the doped-Ce3+enhanced the spectra intensity significantly. Optimalconcentration of KNaCa2(PO4)2:xCe3+, yTb3+is x=0.01, y=0.16. The experimental resultsshow that the KNaCa2(PO4)2:Ce3+, Tb3+is single host phosphor with superior propertiesfor white light emitting UV-LED.(3) A series of orange reddish emitting phosphors of KNaCa2(PO4)2:Sm3+were synthesizedvia conventional solid-state reaction, and its photoluminescence properties wereinvestigated. The excitation spectra of KNaCa2(PO4)2:Sm3+phosphors reveal intensiveexcitation bands at402nm, which match with near-UV LED chips. The emission spectraof the phosphors exhibit three peaks composed of emission peak at569,601and648nm,respectively, due to the4G5/2â†'6HJ/2(J=5,7,9) transitions of Sm3+. The decay lifetime ofthe phosphors doped with different Sm3+amounts was analyzed. The effect of thecompensators Li+on the emission intensity of the phosphor was also investigated. Theintegral intensity of the emission spectrum for KNaCa1.96(PO4)2:0.02Sm3+,0.02Li+phosphor excited at402nm is about1.2times stronger than that of Y2O2S:Eu3+excitedat350nm. (4) A series of blue-emitting phosphors Eu2+-doped KNaCa2(PO4)2were synthesized bysolid-state reaction and the luminescence properties of KNaCa2(PO4)2:Eu2+phosphorswere investigated. This phosphor shows strong excitation band250-450nm, and a broadand asymmetry emission band. The emission intensity of KNaCa1.99(PO4)2:0.01Eu2+wasfound to be85%under excitation at365nm as high as that of BAM:Eu.