Preparation And Properties Of Eu³⁺ Doped Molybdate Red Luminescent Materials

In this paper,NaLa（MoO₄）₂,ZnMoO₄and CaRe₂（Mo O₄）₄（Re=Y,Gd）were used as the matrix materials.With the additives of glutamic acid（GA）,the high-efficient red fluorescent powder with regular morphology and uniform particle size were prepared by hydrothermal synthesis.The main work and results are as follows:（1）Olivine-like NaLa（MoO₄）₂:Eu³⁺red phosphors were synthesized by the hydrothermal method with L-glutamic acid as additive.The effects of the amount of glutamic acid（GA）,the molar ratio of La³⁺/Mo O₄^2-and the hydrothermal reaction time on the morphology,size and luminescent properties of the final synthesized samples were investigated in detail.Furthermore,the growth mechanism of such olivine-like red phosphors was proposed.The results show that,the best doping concentration of Eu³⁺in Na La（Mo O₄）₂:Eu³⁺is 35%.The concentration quenching mechanism of Eu³⁺is mainly the dipole-dipole interaction.The CIE coordinates of Na La_0.65（Mo O₄）₂:0.35Eu³⁺red phosphors（0.6545,0.3350）are closest to the standard red light points（0.67,0.33）and the fluorescence lifetime is 336.04μs.（2）Spherical NaLa（MoO₄）₂-ZnMoO₄:Eu³⁺bimolybdate matrix materials were prepared by hydrothermal method with L-glutamic acid as additive.The effects of glutamic acid（GA）,La³⁺/Mo O₄^2-molar ratio,hydrothermal reaction time and Zn Mo O₄doping amount on the morphology,size and luminescent properties of the synthesized samples were investigated.The results show that when the doping amount of Zn Mo O₄in 4 mmol Na La（Mo O₄）₂is 0.10mmol,the spherical Na La（Mo O₄）₂-Zn Mo O₄:Eu³⁺red phosphors possesses the most uniform morphology.Furthermore,the growth mechanism of such spherical red phosphors was proposed.The optimal doping concentration of Eu³⁺in spherical Na La（Mo O₄）₂-Zn Mo O₄:Eu³⁺is 35%.The CIE coordinates of Na La_0.65（Mo O₄）₂-Zn Mo O₄:0.35Eu³⁺red phosphors（0.6467,0.3353）are closest to the standard red light points（0.67,0.33）and the fluorescence lifetime is71.15μs.（3）CaRe₂（MoO₄）₄:Eu³⁺（Re=Y,Gd）red phosphors were prepared by hydrothermal method with L-glutamic acid as additive.The effects of glutamic acid（GA）addition on the morphology and luminescent properties of Ca Y₂（Mo O₄）₄:Eu³⁺and Ca Gd₂（Mo O₄）₄:Eu³⁺were studied in detail.It is found that when the amount of GA in 2 mmol Ca Y₂（Mo O₄）₄:Eu³⁺is 0.2g,the sample Ca Y₂（Mo O₄）₄:Eu³⁺is a hexagonal nano-sheet with smooth surface.As the amount of GA in 2 mmol Ca Gd₂（Mo O₄）₄:Eu³⁺is 0.4 g,the sample Ca Gd₂（Mo O₄）₄:Eu³⁺exhibits the bipyramid structure.Moreover,the optimum doping concentration of Eu³⁺in Ca Re₂（Mo O₄）₄:Eu³⁺（Re=Y,Gd）is 45%.The CIE coordinates of Ca Y_1.1（Mo O₄）₄:0.9Eu³⁺red phosphors（0.6318,0.3352）and Ca Gd_1.1（Mo O₄）₄:0.9Eu³⁺red phosphors（0.6344,0.3348）are closest to the standard red light points（0.67,0.33）.