Preparation And Luminescence Properties Of La₂Mo₃O₁₂:Eu³⁺ Red Phosphor For White LED

White LED has the advantages of high light efficiency,long life,low energy consumption and environmental friendliness,which is regarded as the fourth generation lighting source after incandescent lamp,fluorescent lamp and high intensity gas discharge lamp.At present,the white LED used widely in the market consists of YAG:Ce³⁺ yellow phosphor and blue InGaN chip,in which the white light is obtained by the mixing of yellow and blue components.Because of the lack of red light components,the traditional white LED has high color temperature and low color rendering index?CRI?.Another way to obtain white LED is to use the near ultraviolet?NUV?LED chip to excite red,blue and green tri-color phosphors.At present,the technology of blue and green phosphor is relatively mature,while searching for red phosphors with low cost,high brightness,stable performance and good color rendering index is the focus of research.Molybdate has good chemical stability and the?MoO₄?^2-ions contained therein can transfer energy effectively.Therefore,we prepared red phosphors using La₂Mo₃O₁₂ as the matrix and Eu³⁺ as the activated center.The Li⁺ and Ba²⁺ ions were used as sensitizers respectively.And systematic researches of the luminescent properties were carried out.The main contents of this paper are as follows:?1?La₂Mo₃O₁₂:Eu³⁺ red phosphors were prepared by different processes,such as sol-gel method,solid state reaction method,hydrothermal method and co-precipitation method.The structure,morphology and luminescent properties of the phosphor prepared by different methods were compared.It is found that there is a little impurity in the samples prepared by solid-state reaction,while all other methods can get pure La₂Mo₃O₁₂:Eu³⁺.Under the monitoring wavelength of 615 nm,the samples prepared by hydrothermal method and sol-gel method show wide excitation peaks near 360 nm,which matches the commercial high-power near UV LED chip.The samples show great red emission at UV and blue light excitation.?2?A series of La₂Mo₃O₁₂:Eu³⁺ red phosphors were prepared by hydrothermal method.The effects of Eu³⁺ doping concentration and post heating treatment temperature on the structure,morphology and luminescent properties were investigated.It is found that the size of particles and the intensity of fluorescence emission increase with the increasing of the post heating treatment temperature.It is also found that the excitation wavelength has an important effect on the concentration quenching effect.?3?La₂Mo₃O₁₂:Eu³⁺ red phosphors were prepared by sol-gel method.The effects of sintering temperature on the structure,morphology and luminescent properties were studied.It is found that some impurity phases appear at 900 and 1000 °C.The particle size of samples increase with the increase of sintering temperature.And the samples sintered at 800 °C exhibit the strongest fluorescence emission under UV excitation.?4?The samples were co-doped with Li⁺ and Ba²⁺ ions respectively.The effects of doping concentration of Li⁺ and Ba²⁺ on the structure,morphology and luminescent properties were studied.It is found that both Li⁺ and Ba²⁺ ions have obvious fluxing effect.When the doping amount of Li⁺and Ba²⁺ is 15 mol%and 3 mol%respectively,the emission intensity of the sample is about 2 times than that of the undoped sample.With the further increase of Li⁺ and Ba²⁺ doping amount,the concentration quenching effect appears.The color coordinates of each group are near?0.65,0.34?,which is close to the standard red light?0.67,0.33?,indicating the high color purity of the samples.