Synthesis And Luminescent Properties Of Rare-earth Doped Fluorescent Material Ca₉Al（PO₄）₇for White LEDs

In this paper, tri-phosphor and single matrix white phosphor were fabricated byhigh-temperature solid-stated method with Ca9Al(PO4)7as a substrate doped Eu2+, Dy3+, Ce3+,Tb3+or Sm3+. The luminescent properties of the materials were analyzed with the emissionspectrum, excitation spectrum, the color coordinates and other methods by changing thedoping concentration, adding the charge compensation or sensitizer. Theconcentration quenching and energy transfer phenomena occurred during the light emittingprocess were discussed. The results were given as follows.(1) The red phosphor of Ca9Al(PO4)7:Sm3+was synthesized and its excitation peak waslocated at403nm. Under the excitation of403nm, four emission peaks were appeared, and564nm corresponded to the4G5/2â†'6H5/2transition of Sm3+,605nm corresponded to the4G5/2â†'6H7/2transition of Sm3+,650nm corresponded to the the4G5/2â†'6H9/2transition ofSm3+,712nm corresponded to the the4G5/2â†'6H11/2transition of Sm3+. The strongestemission peak was605nm and the sample was red. The best doping concentration of Sm3+was1%.(2) The green fluorescent material of Ca9Al(PO4)7:Tb3+was prepared. The excitationspectrum in the350~380nm range was stronger and the peak of the excitation spectrum waslocated at377nm. The emission spectrum composed of four emission peaks which were491nm,545nm,589nm and623nm and corresponded to the5D4â†'7F6,5D4â†'7F5,5D4â†'7F4and5D4â†'7F3level transition of Tb3+. The strongest emission peak was545nm, and the samplewas green light. At last, the methods to improve the luminescence intensity were discussed bychanging the doping concentration of Tb3+, adding charge compensation (Li+, Na+, Ka+) orsensitizer Ce3+.(3) The blue phosphor of Ca9Al(PO4)7:Eu2+was synthesized. The emission spectra of thesamples under the excitation of278nm showed a broadband emission and its emission peakwas located at445nm which belonging to4f65d1-4f7characteristic transition emission of Eu2+.The influence on the luminescence intensity of the doping concentration of Eu2+ion was investigated. The optimal doping concentration was1%. The mechanism of concentrationquenching was interaction between electric multipole and electric multipole.(4) The luminescence properties of Ca9Al(PO4)7:Ce3+,Dy3+which was single matrixwhite phosphor were investigated. Under the excitation of268nm, the emission spectra ofCa8.1Al(PO4)7:0.08Ce3+,0.02Dy3+was composed of the emission band of Ce3+(which was350nm-450nm) and the emission peaks of Dy3+(which were483nm and574nm). Thesample was white light. The effects on the luminescence properties of the concentration ofCe3+and Dy3+were analyzed. The best doping concentration of Ce3+and Dy3+was8%and2%. At last, the energy transfer from Ce3+to Dy3+was discussed.