Synthesis And Properties Research Of LiLa?MoO₄?₂ Red Phosphor

White LED are widely used for their long lifetime,low energy consumption and high luminous efficiency.There are some disadvantages of white LED,such as red light deficiency,higher color temperature and low color rendering index,which limit its development to a higher field.Therefore,a red phosphor with high stability and high efficiency is developed to reduce the color temperature of white LED and enhance the color purity to meet the increasing high performance demands in daily life and production.In many rare-earth luminescent materials,rare earth doped molybdate red phosphors have excellent physicochemical stability and strong absorption of ultraviolet light,so it is a potential LED luminescent materials.Due to high production cost,insufficient luminous intensity and efficiency and other problems that can not meet the requirements for use.Therefor,these samples were characterized by Thermogravimetry-Differential thermal analysis?TG-DTA?,X-ray diffraction?XRD?,scanning electron microscope?SEM?,and fluorescence spectroscopy.The synthesis parameters and fluorescence performance were optimized.LiLa?MoO₄?₂:Sm³⁺phosphors were synthesized by citric acid solution combustion method.The LiLa?MoO₄?₂:Sm³⁺phosphor with high purity and excellent luminescence properties were synthesized.The optimum synthetic process conditions were:the synthesis reaction temperature was 700°C,the reaction time was about 1 hour and the mixture ratio of C₆H₈O₇ to LiLa?MoO₄?₂ was 1.5 to 1.The strongest characteristic excitation peak of LiLa?MoO₄?₂ phosphor was located at 403 nm,which belonged to the ⁴G_5/2?⁶H_9/2 characteristic transition of Sm³⁺.The strongest characteristic emission peak of LiLa?MoO₄?₂ phosphor was located at 648 nm,which belonged to the ⁴G_5/2?⁶H_9/2 characteristic transition of Sm³⁺.The doping concentration of Sm³⁺had considerable influence on the luminescence intensity.When the doping concentration of Sm³⁺ranged from 0 to 9 mol%,the emission intensity increased with the increasing of concentration.The luminescence intensity reached its highest when the concentration of Sm³⁺reached at 5 mol%,then the emission intensity declined and concentration quenching effect ultimately occurred.In order to further improve the fluorescence performance of LiLa?MoO₄?₂:Sm³⁺,rare earth Eu³⁺and Y³⁺were selected for doping modification.The results showed that Eu³⁺was beneficial to improve its luminescence performance,enhance and broaden the characteristic excitation peak of Sm³⁺at 403 nm.The emission peak was at 618 nm,which was the characteristic transition ⁵D₀?⁷F₂ of Eu³⁺.The emission intensity increased with the increase of Eu³⁺concentration,while the emission peak of Sm³⁺decreased.The color coordinates of co-doped Eu³⁺samples moved to the standard red color coordinates.The fluorescence life was shortened.There may be energy transfer from Sm³⁺to Eu³⁺.Y³⁺doping significantly enhanced the excitation intensity and emission intensity of the samples.When the doping concentration of Sm³⁺ions was 9mol%,the color coordinate was?0.654,0.3456?.The fluorescence enhancement was the most significant when the concentration of Y³⁺reached at 5 mol%,then the emission intensity declined and concentration quenching effect occurred.According to ion proximity and the basic conditions of ion substitution,the corresponding ions in LiLa?MoO₄?₂:Sm³⁺lattice were substituted by doping Bi³⁺,Ag⁺and W⁶⁺,respectively.The ion doping concentration was optimized and its effects on the luminescence properties of the synthesized samples were investigated.The results showed that the doped Bi³⁺can enhance the characteristic emission intensity of Sm³⁺.The doping of Bi³⁺can play a role in energy transfer and increase the fluorescence lifetime.The fluorescence enhancement was the most significant when the concentration of Bi³⁺reached at 1 mol%.Although Ag⁺and W⁶⁺can also enhance the luminescence,the fluorescence lifetime of the samples was reduced.When the Ag⁺and W⁶⁺doping concentrations were 1 mol%and 20 mol%respectively,the fluorescence performance was the best.The above research results have reference value for the improvement of fluorescence performance of LiLa?MoO₄?₂:Sm³⁺and the realization of commercial application.