Synthesis And Luminescence Properties Of Ions Doped YAG:Ce³⁺ Powder

White LED （Light-Emitting Diodes） has high-profile prospects in the lighting market dueto the advantages of its all-solid-state, low power consumption, high luminous efficiency, lowradiation, long service life and almost all spectrum concentrated in the visible light spectrum,which is considered with the greatest potential to replace incandescent, tungsten andfluorescent merchandise in future. The property of YAG:Ce³⁺excited by Blue-ray and UVplays a vital role in the realization of the excellent performance of white LED. In this paper, theeffects of microwave homogeneous precipitation and a spray-drying method, combined withthe calcination-assisting fluxes and ion doping factor on the crystal structure, morphology andoptical properties of YAG:Ce³⁺phosphor were investigated and the main research work aresummarized as optimize of the synthesis process and ion doping improvement of luminescentproperties below:（1） The well-dispersive single-phase YAG:Ce³⁺phosphors with mean size mostly at2μmwere synthesized by microwave irradiation combined with spray-drying method in the presenceof fluxes. The effect of fabrication conditions on calcination process and properties ofYAG:Ce³⁺phosphors was discussed. The results show that spherical-like YAG precursor couldbe obtained by a combination of two methods above. Conventional drying method was replacedby spray-drying, which can reduce the reunion of the phosphors significantly, get a betterdispersibility and the small size of particles. So it is beneficial for luminescent properties andcoating of phosphor. Good dispersion, small size and uniform precursor particles can beobtained with0.0125mol/L solution concentration of precursor.The single-phase YAG:Ce³⁺phosphors were synthesized with fluxes NaF, mixed fluxconsisting of NaF and H₃BO₃, BaF₂, and mixed flux consisting of BaF₂and H₃BO₃, which wereblended with precursors. The effects of type, dosage of flux and composition of mixed flux onmorphology, dispersity and luminescence performance of YAG:Ce³⁺particles were investigated.Phase-pure YAG was prepared at the calcination temperature of1150℃. The crystallization andluminescence intensity were obviously improved with increasing content of NaF flux, andblue-shift in the luminescence spectra was found. The optimal luminescence intensity ofYAG:Ce³⁺phosphors was obtained on the condition of containing6wt%NaF. The emission intensity was higher with mixed flux than that with NaF. And the effect of composition ofmixed flux on luminescence performance of YAG:Ce³⁺phosphors was investigated, themaximum emission intensity was obtained with4wt%NaF and2wt%H₃BO₃. The calcinationtemperature depressed to1370℃with BaF₂and mixed flux consisting of BaF₂and H₃BO₃. Theoptimal luminous intensity of the YAG:Ce³⁺phosphor powders are obtained on the condition ofcontaining6wt%BaF₂. The phosphor doped with the mixture of1wt%BaF₂and1wt%H₃BO₃has higher luminous intensity. Calcination in the reductive atmosphere can inhibit thedecomposition of CO₃^2-and Ce³⁺oxidized, which ensure the property of YAG:Ce³⁺.（2） The dispersibility and luminous performance of YAG:Ce³⁺phosphor are different fordifferent qualities of Ce³⁺. The peaks of the emission spectra are essentially the same, while theintensity of emission spectra is strongest on the condition of doping with4%Ce³⁺. Si⁴⁺dopedYAG:Ce³⁺phosphor has better crystallinity and worse dispersibility compared with YAG:Ce³⁺phosphor, which is more serious as the amount of Si⁴⁺is increasing. Mono-phase YAG wasobtained when x in the general formula Y_2.88Ce_0.12Al_5-xSi_xO₁₂was below0.3, and furtherincrease of silicon nitride content in the starting mixture led to precipitation of Y2Si2O7. Theemission spectra of Si⁴⁺doped YAG:Ce³⁺phosphor becomes widener and its intensity increasesby almost40%. YAG:Ce³⁺phosphor with different content of Pr³⁺will lead to differentphosphor with respect to different particle morphology, dispersion and fluorescence spectra.Moreover, compare to YAG:Ce³⁺phosphor without Gd³⁺, phosphor with different content ofGd³⁺show worse particle homogeneity, and better uniformity. With the changing concentrationof Pr³⁺, the emission spectrum of the peak position is essentially the same, but its intensity isconstantly changing. There are two main emission peaks in this YAG that were doped withpraseodymium phosphor emission spectra. The first was Ce³⁺emission peak, and the secondemission peak located around610nm (of the Pr³⁺emission peak). Final results show that thestrongest fluorescence intensity of Pr³⁺doped mole percent of1%, With adding rare earth ionGd³⁺, red-shifted will occur in relation to the emission wavelength of YAG:Ce³⁺phosphor. Inthat case, red light-emitting ingredient of the white LED will be increased, and its strength willchange along with the changing intensity. Final result shows that with0.2%concentration ofGd³⁺, its emission peak reaches the strongest point, followed by1%,2%,0.67%respectively.