Spectral Regulation Of β-Ca₃（PO₄）₂ Type Phosphor Based On Ion Substitution And Energy Transfer

It is the most popular method for synthesizing white LEDs that near-ultraviolet（NUV）LED chip combined with a single matrix phosphor.Because its high color rendering and adjustable color and color temperature.Theβ-Ca₃（PO₄）₂ type phosphor with polycationic crystal structure and can be substituted by others cation.After doping the rare earth ion Eu²⁺,phosphors of different luminescent colors can be obtained and achieved spectral control.In addition,color-tunable luminescence can also be achieved by the energy transfer between Eu²⁺-Mn²⁺after doped the Mn²⁺.In this paper,a series ofβ-Ca₃（PO₄）₂ type phosphors were synthesized by thehightemperaturesolid-statemethod:bluish-violetemitting Sr_9-xIn（PO₄）₇:xEu²⁺phosphors,theemissioncolortuned Sr_8.97In_1-yLu_y（PO₄）₇:0.03Eu²⁺phosphors,Ca₁₀K（PO₄）₇:Eu²⁺,Mn²⁺and Ca₉SrK（PO₄）₇:Eu²⁺,Mn²⁺phosphors,and their phase,luminescence properties,energy transfer between co-doped ions were studied.The specific research contents are as follows:（1）A bluish-violet emitting Sr_9-xIn（PO₄）₇:xEu²⁺phosphors were synthesized by the high temperature solid-state method.Under 365 nm excitation,the emission spectrum of the sample shows two broad bands with peaks at 410 nm and 630 nm,respectively,which is corresponds to the4f⁶5d¹-4f⁷ transitions of Eu²⁺and due to the Eu²⁺occupying{Sr（1）,Sr（3）,Sr（4）,Sr（5）}and Sr（2）sites.By analyzing the fluorescence decay curve of Sr₉In（PO₄）₇:Eu²⁺,which indicates that energy transfer are existed among Eu²⁺ions.The concentration quenching is caused by the energy transfer among the near-neighbor ions.（2）The emission color tuned Sr_8.97In_1-yLu_y（PO₄）₇:0.03Eu²⁺phosphors were synthesized by the high temperature solid-state method.Under 365 nm excitation,the emission spectrum contains two emission bands.When the Lu³⁺undoped,the emission spectrum only has one emission band at 410 nm.When the Lu³⁺doped,the emission spectrum shows another emission band at 520 nm.With the continuous introduction of Lu³⁺into the crystal lattice,the emission intensity of the band located at 410 nm decrease and the band located at 520 nm increase gradually.Meanwhile,the illuminating color changed from blue-violet to white to yellow.The emission bands located at 410 nm and 520 nm are originted from two different luminescence centers of Eu²⁺,which can be verified by different excitation spectra.（3）Ca₁₀K（PO₄）₇:0.05Eu²⁺,xMn²⁺and Ca₉SrK（PO₄）₇:0.05Eu²⁺,yMn²⁺phosphors were synthesized by high temperature solid-state method.The emission spectra of Ca₁₀K（PO₄）₇:Eu²⁺and Ca₉SrK（PO₄）₇:Eu²⁺varied at different excitation wavelengths of 300 and 350 nm.This is due to the difference in excitation wavelength and the relative intensity of each emission peak.Therefore,the shape is different after spectral overlay;The fixed excitation wavelength is 300 nm,one Ca ion is substituted by one Sr ion,or incorporation Mn ion,the emission spectra of the sample are also different,which is caused by energy transfer between different emission bands.Through the analysis of emission spectrum and fluorescence lifetime,it is found that the high energy state Eu transmits part of the energy to the low energy state Eu,and both the high energy state and the low energy state Eu transfer energy to Mn,and the high energy state Eu transmits energy to Mn more effectively.