Study On Preparation And Properties Of Rare Earth Vanadate

In this thesis,the LuVO₄:Eu³⁺phosphors were prepared by the hydrothermal method,and the properties of samples prepared under different synthesis conditions were studied.In preparing LuVO₄:Ln³⁺(Ln³⁺=Dy³⁺,Eu³⁺,Tm³⁺/Dy³⁺,Eu³⁺/Dy³⁺/Eu³⁺/Tm³⁺)phosphors,the effects of energy transfer mechanism was studied.White light emission was successfully achieved through the phosphors composite g-C₃N₄/LuVO₄:Eu³⁺and g-C₃N₄/LuVO₄:Dy³⁺,Eu³⁺and by adjusting the ratio of them was established.Hydrogen production was achieved by YVO₄/g-C₃N₄ and YVO₄/g-C₃N₄/Au acting as decomposition water catalysts and researched catalytic mechanism.The details are as follows:1.The LuVO₄:Eu³⁺phosphor was prepared by the hydrothermal method.The optimal doping concentration of Eu³⁺,the optimum reaction time,the optimum reaction temperature and the optimum reaction pH are 5%,48h,180°C and 9.0,respectively,by their fluorescence spectroscopy.The space-group of the LuVO₄:Eu³⁺belongs to I4₁/amd by XRD analysis.The scanning electron microscopy?SEM?images of the LuVO₄:Eu³⁺shows about 66 nm in the edge length.2.LuVO₄:Ln³⁺(Ln³⁺=Dy³⁺,Eu³⁺,Tm³⁺/Dy³⁺,Eu³⁺/Dy³⁺/Eu³⁺/Tm³⁺)phosphor samples were prepared by hydrothermal method.It shows the scanning electron microscpoy?SEM?images of the LuVO₄:Ln³⁺(Ln³⁺=Dy³⁺,Eu³⁺,Tm³⁺/Dy³⁺,Eu³⁺/Dy³⁺/Eu³⁺/Tm³⁺)phosphor samples with about 67 nm in edge length and about 50 nm in width,respectively.Moreover,the energy transfer from Dy³⁺and Eu³⁺in LuVO₄ is via dipole-dipole interaction.According to the PL spectra of LuVO₄:1%Dy³⁺,1%Eu³⁺and LuVO₄:1%Dy³⁺,1%Eu³⁺,3%Tm³⁺,the CIE coordination were calculated as?0.316,0.363?and?0.331,0.334?,respectively.LuVO₄:1%Dy³⁺,1%Eu³⁺?0.316,0.363?and LuVO₄:1%Dy³⁺,1%Eu³⁺,3%Tm³⁺?0.331,0.334?phosphor are closest to white light?0.333,0.333?.Under a forward-bias current of 60,100,150,200 mA,respectively,the correlated color temperatures?CCT?of LuVO₄:1%Dy³⁺,1%Eu³⁺-based W-LED device are 8163,7778,8968,and 11237K,respectively,the color rendering index?Ra?are 60.1,71.3,74.4,and 77.7,respectively.And the correlated color temperature?CCT?of LuVO₄:1%Dy³⁺,1%Eu³⁺,3%Tm³⁺-based W-LED device are 2133,2130,2170,and 2190K,respectively,the color rendering index?Ra?are 52.4,54.3,55.6 and 55.8,respectively.3.The LuVO₄:Eu³⁺and the LuVO₄:Dy³⁺,Eu³⁺phosphors were synthesized by the hydrothermal method,and g-C₃N₄ was synthesized by the condensation of melamine method.A series of color-adjustable g-C₃N₄/LuVO₄:Eu³⁺and g-C₃N₄/LuVO₄:Dy³⁺,Eu³⁺composite phosphors were synthesized by the simple composite method.According to the study of CIE color coordinates,the optimal ratio of g-C₃N₄ and LuVO₄:Eu³⁺?CIE:0.326,0.269?is 50%:50%and the optimal ratio of g-C₃N₄ and LuVO₄:Dy³⁺,Eu³⁺?CIE:0.331,0.339?is 60%:40%,and their CIE coordination are all closer to the white light?0.333,0.333?.4.The g-C₃N₄ was synthesized by the heating urea.The binary composite photocatalyst YVO₄/g-C₃N₄ was synthesized by the hydrothermal method.The YVO₄/g-C₃N₄/Au ternary composite photocatalyst was synthesized through the Au nanoparticles deposited to the YVO4/g-C₃N₄ by the photodeposition.According to the performance of different catalysts for H2production,the hydrogen production rate of 35%YVO₄/g-C₃N₄ is 6.1 times that of pure g-C₃N₄,and the hydrogen production rate of 35%YVO4/g-C₃N₄/Au photocatalyst is 29.6 times that of pure g-C₃N₄.