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Influence Of Alkali(Alkaline-earth)Metal On White Light Emissions Of Eu3+:Dy3+:Y2O3 Nanophosphors

Posted on:2018-04-26Degree:MasterType:Thesis
Country:ChinaCandidate:H B ZhangFull Text:PDF
GTID:2310330515453376Subject:Optics
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The functional materials doped rare earth ions have comprehensive applications in many fields,such as the superconductive material and permanent magnetic material,and so on.They also show the important application value in the optics field,including white light LED and laser,etc.Therefore,it is of great significance to investigate the optimal preparation technology of luminescence materials doped rare earth and the analysis of photoluminescence mechanism in depth.The main contents of this thesis are as follows:First of all,two series of nanophosphors with single-or co-doped Eu3+ and Dy3+ions,that is,Eu3+:Dy3+:Y203 and Eu3+:Dy3+:XyY(2-y)03(X= Li+,Na+,K+,Mg2+,Ca2+,Sr2+)have been prepared by the high temperature solid reaction method,and the preparation technology and parameters are optimized.The measure results of XRD show that main diffraction peaks of two series nsnophosphors are coincident with those of the standard card of Y2O3 crystal,no matter rare earth ions or alkali/alkaline-earth metal ions are doped,indicating that a small amount of dopants do not affect clearly the crystal structure of the nanophosphors.The observation results of SEM show that all the phosphors are uniform particles with the average size of 40-50 nm.Secondly,the excitation and emission spectra of single-and co-doped Eu3+:Dy3+:Y2O3 nanophosphors are measured systematically,and the white light characteristics including CIE coordinate and color temperature are calculated and analyzed.Under the excitation of 330 nm,there exist the intense violet,blue and green emissions respectively at 410,488 and 573 nm from Dy3+:Y2O3 nanophosphors,moreover,there has the intense red emission at 612 nm from Eu3+:Dy3+:Y2O3 except above three color emissions.The CIE value of the 1.0Eu3+:1.0Dy3+:Y2o3 nano-phosphor is(0.32,0.33)and the color temperature is about 5129 K,implying that Y2O3 nanophosphor co-doped the europium and dysprosium ions is an ideal phosphor material for white light LED.The influence of the Dy3+ concentration and the concentration ratio between Dy3+ and Eu3+ ions on the photoluminescence properties is further discussed.The optimum Dy3+ doping concentration is 1 mol%and the Dy3+:Eu3+ concentration ratio is 1:1.At the same time,the photoluminescence mechanisms of single-and co-doped Eu3+:Dy3+:Y2O3 nanophosphors,especially the energy transfer process between europium and dysprosium are analyzed.The effect of sinter temperature on PL characteristics is further discussed and the preparation technology and parameters are optimized.Finally,the influence of alkali(alkaline-earth)metal ions on photoluminescence characteristics of Eu3+:Dy3+:Y2O3 nanophosphor is analyzed detailedly.When the monitoring wavelength is selected as 612 nm,the doping of three kinds of metal ions Na+,Mg2+ or Sr2+ will enhance the peak intensities of the excitation spectra belonging to Eu3+:Dy3+:Y2O3 nanophosphors,and the effect of alkali metal Na+ ions is the most significant,which indicates that the red emissions of Eu3+:Dy3+:Y2O3 nanophosphors will be improved obviously after Na+ ions are codoped into phosphors and the optimized Na+ concentration is 15 mol%.Moreover,the excitation peaks of the phosphors codoped Eu3+ and Dy3+ at 330 nm become more intense after Sr2+ ions are codoped into phosphors,implying that the Sr2+ ion has a very positive effect on the enhancement of white light emission.When the Sr2+concentration is 8 mol%,the white light emission from Eu3+:Dy3+:XyY(2-y)O3 nanophosphor is the most ideal,and CIE coordinate is(0.33,0.32)and the color temperature is 6220 K.The intrinsic reason lies in that Sr2+ ion hinders the energy transfer from Dy3+ ion at 4F9/2 level to Eu3+ ion at 5D0 level,witch is equivalent to enhance the PL intensities of Dy3+ ion at blue and green bands and the performances of the white light emissions from Eu3+:Dy3+:Y2O3 nanophosphors are also improved.
Keywords/Search Tags:Eu3+, Dy3+, Y2O3 nanophosphors, Alkali(alkalin-earth)metal, Excitation and emission spectra, White light emission, Energy transfer
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