Study On Preparation And Optical Performance Of Phosphors For White LED

In this thesis,the rare earth doped NaGd?MoO₄?₂ luminescent materials were synthesized.Their optical properties have been investigated in details.The main research contents can be summaried as follows:1.A series of NaGd?MoO₄?₂: 7% Eu³⁺ phosphors were prepared by hydrothermal method.The influences of hydrothermal time,the amount of surfactant sodium citrate,MoO₄^2-:Gd³⁺ and pH of reaction system on the morphology and luminescent property of samples were studied.The results showed that pH = 5,reaction time 24 h,the amount of sodium citrate was 0.7 mmol and MoO₄^2-: Gd³⁺ = 3:1 are the optimum conditions.Under the conditions,the samples have good crystallinity,homogenous shuttle morphology and good luminescence.2.The NaGd?MoO₄?₂: xEu³⁺?x=10%,20%,30%,40%?and NaGd?MoO₄?₂: 7%Eu³⁺,ySO₄^2-/BO₃^3-phosphors were synthesized via hydrothermal method.The emission spectra showed that the emission intensity was the highest when the doping concentration of Eu³⁺ was 30% in NaGd?MoO₄?₂: x Eu³⁺.The effects of concentration of doping SO₄^2-/BO₃^3-on the luminescence properties of NaGd?MoO₄?₂: 7%Eu³⁺,ySO₄^2-/BO₃^3-phosphor were studied.3.The NaGd?MoO₄?₂: Tb³⁺ /Eu³⁺,Tb³⁺ /Eu³⁺,Tb³⁺,Tm³⁺ phosphors were synthesized by microemulsion-hydrothermal method.The effect of doping concentration on luminescent properties of the samples was studied,and the energy transfer from Tb³⁺ to Eu³⁺ was also discussed in detail.The pseudo-white light emission can be obtained by adjusting the concentration of Eu³⁺,Tb³⁺,Tm³⁺.4.The Na Gd?MoO₄?₂: Dy³⁺/Dy³⁺,Eu³⁺ tetragonal crystals were synthesized by hydrothermal method and the samples were also characterized.The energy transfer process from Dy³⁺ to Eu³⁺ in NaGd?MoO₄?₂: Dy³⁺,Eu³⁺ was studied by fluorescence spectroscopy,energy transfer efficiency and fluorescence lifetime.The yellow to white to pink light color shift can be achieved by adjusting the concentration of Dy³⁺,Eu³⁺.