Prepaparation And Luminescence Properties Of Y₃（Al,Ga）₅O₁₂:Ce³⁺ Phosphor

In this dissertation,a series of Y₃（Al,Ga）₅O₁₂:Ce³⁺(YAGG:Ce³⁺)、Y_2.94-xLa_x Al₄GaO₁₂:Ce³⁺(YLaAGG:Ce³⁺)、Y_2.94-xGd_x Al₄GaO₁₂:Ce³⁺(YGdAGG:Ce³⁺)、Y_2.94-xTb_x Al₄GaO₁₂:Ce³⁺(YTbAGG:Ce³⁺)and Y_2.94-xLu_xAl₄GaO₁₂:Ce³⁺(YLuAGG:Ce³⁺)phosphors were prepared by the coprecipitation-molten salt method.X-ray diffraction,photoluminescence spectrophotometer（PL）and SEM were used to characterize the samples.The main research contents and results in this thesis include the following three aspects:1.The effects of titration method,concentration ratio of mixed precipitant,pH value of solution,type and proportion of molten salt,sintering temperature and holding time on phase structure,luminescence properties and particle morphology of YAGG:Ce³⁺phosphors were studied.The suitable process conditions for the synthesis of YAGG:Ce³⁺phosphors by coprecipitation-molten salt method were determined.The results indicate that the co-precipitation precursor was prepared by using NH₃·H₂O and NH₄HCO₃ solution with volume ration of 1:1 and concentration of 1 mol/L as the mixed precipitant.The metal ion solution was titrated with the precipitant by co-drop titration,the pH of the solution was maintained at 7.5.NaCl:KCl:KF·2H₂O with molar ratio of 1:1:0.3 was used as molten salt,and the holding time was 3.5 hours of 1250℃.The prepared sample has the highest luminous intensity,good dispersion and uniform particle size of about 1mm.2.The effect of Ga³⁺substitute Al³⁺on lattice structure and luminescence properties of Y₃Al_5-xGa_xO₁₂:Ce³⁺samples were studied.The results indicate that Ga³⁺can completely substitute Al³⁺to form a solid solution.With the increase of the amount of Ga³⁺substituting Al³⁺,the XRD diffraction peaks of the samples shifted to a small angle,but the cubic crystal structure was still maintained.The peak wavelength of the emission spectrum shows a progressive blue-shift from 530 nm at x=0 to 500 nm at x=4.When x=1,the sample has the highest luminous intensity,with a peak wavelength at 516 nm.When Ga³⁺content is 5,the sample does not show emission.3.The effects of La³⁺,Gd³⁺,Tb³⁺,Lu³⁺substituting Y³⁺on the phase structure and luminescence properties of Y_3-x-x Al₄GaO₁₂:Ce³⁺samples were studied.The results indicate that the maximum substitution amount of La³⁺substituting Y³⁺into the YAGG lattice is x=0.3,and the emission spectrum shows a red shift with about 6 nm.Gd³⁺,Tb³⁺and Lu³⁺can totally substitute Y³⁺of YAGG without change of the lattice structure.Gd³⁺substituting Y³⁺and the peak wavelength of the emission spectrum exhibited red-shift from 516 nm to549 nm.After the Y_0.44Gd_2.5Al₄GaO₁₂:0.06Ce³⁺sample was packaged into a white LED,the color rendering index（CRI）was 84.6 and the correlated color temperature（CCT）was4565 K.Tb³⁺substituting Y³⁺and the peak wavelength of the emission spectrum showed red-shift from 516 nm to 538 nm.Y_0.44Tb_2.5Al₄GaO₁₂:0.06Ce³⁺sample was packaged into a white LED,the CRI was 83.7 and the CCT was 4971 K.Lu³⁺substituting Y³⁺and the peak wavelength of the emission spectrum showed blue-shift from 516 nm to 497 nm.After mixing the Y_0.44Lu₂Al₄GaO₁₂:0.06Ce³⁺sample with commercial red phosphors,the CRI was 90 and the CCT was 4565 K.