Preparation And Properties Of A New LED Fluorescent Materials

White LED has been widely used because of its green,energy saving and environmental protection.However,the existing white LED still has some shortcomings,such as low luminous efficiency,unstable performance,serious chip heat dissipation and lack of red light part.Phosphors are the key to LEDs.In this paper,using molybdate system phosphors with strong stability,non-metamorphism and easy absorption of ultraviolet light are used to prepare molybdate system phosphors with higher photoelectric intensity after activation of rare earth ions,to replace the red powder Y₂O₃:Eu³⁺commonly used in LED on the market.The YAG:Ce³⁺phosphor prepared by the traditional high temperature solid phase method has the phenomenon of coarse particles and serious agglomeration.The YAG pure phase with smaller particles and better dispersion was prepared by the co-precipitation method and the inorganic salt isolation method.On this basis,the structure of"near ultraviolet purple LED chip+blue/green/red phosphor"was used to fabricate the white light-emitting diode WLED device.The main results are as follows:（1）Y₂MoSiO₈precursor was prepared by high temperature solid phase method,doped with Y₂MoSiO₈:Dy³⁺,Eu³⁺of 12mol%europium ion,3mol%,5mol%,7mol%and9mol%dysprosium ion,and then 1.5wt%NH₄F flux was added to prepare Y₂MoSiO₈:Dy³⁺,Eu³⁺materials.The structure,phase and luminescence properties of the products were studied.The luminescence intensity of Y₂MoSiO₈phosphors doped with Dy³⁺and Eu3+was good.The effects of the concentration of doped rare earth ions Dy³⁺and Eu³⁺on the luminescence properties of phosphors were investigated.The luminescence properties of phosphors increased with the increase of the concentration of doped ions.When the doping concentration of Dy³⁺was 7mol%,the luminescence intensity reached the maximum.（2）Using coprecipitation and inorganic salt isolation of the smaller particles prepared by not reunite dispersed better YAG pure phase,precipitating agent of choice is uniform and stable to produce hydroxyl ions of urea,inorganic salt selection is resistant to high temperature and sodium fluoride salt soluble in water,salt best material ratio of1:3,and calcination temperature as low as 1000℃,the problems of high temperature solid phase sintering and high temperature calcination of large particles are avoided（3）The YAG precursors were doped with certain concentration gradient of cerium ion,bismuth ion and dysprosium ion to study their luminescence properties.The optimal doping concentration ratio of cerium ion and bismuth ion was 4mol%,and the optimal concentration ratio of dysprosium ion and cerium ion was 2mol%.The phosphors had the best properties.The research shows that this method provides a new and environmentally friendly way for the preparation of new LED phosphors.（4）Using self-made Y₂MoSiO₈:Eu,Dy red phosphor,commercial（Ba,Sr）₂Si O₄:Eu green phosphor and Ba Al₁₀O₁₇:Eu blue phosphor as raw materials,the WLED device was prepared by using the structure of"near-ultraviolet purple LED chip+blue/green/red phosphor".