Preparation And Luminescence Properties Of White LED Phosphors

In this paper, Ca10Na(P04)7,Ca10Nao.75K0.25(PO4)7,Ca10K(PO4)7 and Sr3Al2O6 phosphors, doped with Eu3+,Eu2+/Mn2+and Ce3+/Eu2+, were prepared using high temperature solid state technology. The phase structures of the phosphors were examined by XRD and their luminescence properties were studied by fluorescence spectroscopy. The main content is listed as following:Phase composition and fluorescence emission properties of Ca9.95_xNao.75Ko.25(PO4)7: 0.05Eu2+,xMn2+were studied. Due to the existence of double phases with similar crystal structure, the 5d—4f transition of Eu2+ ions in the phosphors emit a fluorescence of wide wavelength with peaks located at 491nm and 540nm respectively. The energy transfer between Eu2+ and Mn2+, together with the occupation of Mn2+ ions at the eight coordination sites in the phosphors make the 4T1 (4G)-6A1 (6S) transition of Mn2+ ions produce red emission peaked at 635nm. The combination of fluorescence combination by Mn2+ and Eu2+ ions results in the emission of white light with color coordinates (0.3335,0.2924), (0.3999,0.3179) and (0.3307,0.2564).We studied the red phosphor of Ca10-xK(P04)7:xEu3+.X-ray diffraction showed that all samples crystallized in the standard Ca10K(P04)7 hexagonal crystal structure, and no secondary phase was observed. Under the excitation at wavelength 393nm, the red emission brought by the 4f-4f transition in Eu3+ was observed, and the strongest emission peak was near 613nm which was caused by the 5D0→7F2 electric dipole transition. By adjusting Eu3+ concentration, color coordinates close to the commercialization of Y2O2S:Eu3+ Phosphor can be obtained.Phase composition and luminescence properties of Ca9.98-x Na (PO4)7:0.02Eu2+,xMn2+ were studied. The results showed that the samples have single phase crystal structure, Eu2+ and Mn2+ ions both occupy the crystal sites of Ca2+ ions, the ranging of the color is from (0.2657,0.4346) to (0.3501,0.3869).Phase composition and fluorescence emission properties of Sr3-x-yAl2O6:xCe3+,yEu2+ were studied. The results showed that the samples have single phase of structure. Under 360nm UV light excitation, Ce3+ ions forms a broad blue emission band with a peak at 434nm. With the energy transfer from Ce3+ ions, Eu2+ ions emit a broad red band with the peak at 517nm. The mixture of the Ce3+and Mn2+ phosphors forms a approximate white light with the CIE Chromaticity (0.2611,0.3313). The phosphors can be excited effectively by UV light in the range of 250-400nm, so they are the potential candidates for single white light-emitting phosphor excited by UV-LED.