Preparation And Characterization Of Rare Earth Ions Doped Ca₂NaMg₂V₃O₁₂ Luminescence Materials

In the environment of the global energy crisis,luminescent materials as relatively large material consumption industries have been paid more attention.LED solid-state lighting device have the many advantages of high efficiency,energy saving,environmental protection and so on,in accordance with the existing environmental conditions,after more than 10 years of development has basically replaced the traditional incandescent lamp,fluorescent lamp and become a new generation of lighting source.The effect of phosphors with red emitting color on the color rendering index and color temperature of white light LED are significant.Vanadate phosphor has the function of wavelength conversion.Under UV wavelength excitation,vanadate phosphors can emit light with different wavelengths.In this paper,Ca₂NaMg₂V₃O₁₂:Re³⁺(Eu³⁺,Dy³⁺,Sm³⁺,Pr³⁺)phosphors were prepared by high temperature solid states method,on the basis of this study.The structure and luminescence of the samples were characterized by X ray diffraction?XRD?,photoluminescence spectra,lifetime and thermal stability.The main experiment contents included as follow:1.The optimum temperature condition for the prepared Ca₂NaMg₂V₃O₁₂:Re³⁺phosphors by high temperature solid state method was 1000 ⁰C.2.The GSAS structure refinement to determine the site of rare earth ions Eu³⁺,Dy³⁺,Sm³⁺ into the crystal lattice.They occupied Ca/Na dodecahedron sites.The crystal is a garnet structure with a coordination number of 8.The refinement lattice constants obtained compared with the standand card was small.The unit cell contraction is caused by the radius of the rare earth ion shorter than the radius of Ca/Na.3.Meanwhile,according to the Gaussian components by fitting the excitation spectrum,the excitation band of Ca₂NaMg₂V₃O₁₂:Dy³⁺,Sm³⁺consists of three peaks?which is ascribed to the energy transition between ¹A₁-¹T₁ and ¹A₁-¹T₂?.Under the excitation of 365nm, Ca₂NaMg₂V₃O₁₂:Re³⁺(Eu³⁺,Dy³⁺,Sm³⁺)samples shown broad emission bands and characteristic emission peaks of rare earth ions.Vanadate phosphors were self-activated fluorescence materials,luminescent properties of self-activated VO₄^3-group with T_d symmetry originates from the charge transition of V-O ions,emission spectra covered 400-700nm,and shows strong broadband emission at 400-575nm.Emission band of Ca₂NaMg₂V₃O₁₂:Eu³⁺shown the range from 575 to 700 nm corresponds to ⁵D₀-⁷F_1,2,3,4 transitions of Eu³⁺.The major peak is located approximately at 607nm?showed strong red light?corresponding to the electric dipole transition ⁵D₀-⁷F₂,the concentration quenching point is 0.07.Ca₂NaMg₂V₃O₁₂:Dy³⁺phosphor shown two emission peaks located at approximately 480nm?blue light?and 575nm?yellow light?corresponding to the ⁴F_9/2- ⁶H_15/2 and ⁴F_9/2-⁶H_13/2 transition,the quenching concentration point is 0.06. Ca₂NaMg₂V₃O₁₂:Sm³⁺phosphor shown that three characteristic emission peaks are attributed to the ⁴G_5/2-⁶H_J/2?J=5,7,9?transition.And the three kinds of phosphor Ca₂NaMg₂V₃O₁₂:Re³⁺(Eu³⁺,Dy³⁺,Sm³⁺)have good thermal stability.The color is tunable by changing the concentration.4.There is energy transfer from matrix to the rare earth ions Eu³⁺,Dy³⁺,Sm³⁺.And energy transfer can be verified through energy transfer efficiency,lifetime,overlapping of excitation spectrum,critical distance and so on.Energy transfer mechanism is the electric dipole-dipole mechanism of the interaction of electric multipole.5.The substituting alkaline earth metal ions in the M₂RMg₂V₃O₁₂?M=Ca,Sr,Ba;R=Na,K, Li?phosphors.The best composition of the phosphor was determined by the photoluminescence spectrum.The results showed that the luminescence intensity of Ca₂NaMg₂V₃O₁₂ was the strongest.