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.