| In this thesis, M2xCa1-xWO4:Yb3+/Er3+(M=Li, Na, K) polycrystalline were preparedby high temperature solid-state method. The influence of doping different kinds andratios of alkali ions into polycrystalline CaWO4:Yb3+/Er3+on its preparation process andup-conversion luminescence properties also have been studied.The sintering reaction and impurity removal temperature range of theM2xCa1-xWO4:Yb3+/Er3+(M=Li, Na, K) polycrystalline synthesize process werecharacterized by TG-DTA determination. XRD and Up-conversion emission spectra testwere used to determine the best sintering reaction condition under which thewell-crystallized sample that has the highest up-conversion intensity were prepared. Theresults of the study showed that900℃,10h is the best sintering reaction condition whiledoping Li+ion;800℃,10h is the best sintering reaction condition while doping Na+ion;800℃,6h is the best sintering reaction condition while doping K+ion.The influence of doped alkali-metal ions into M2xCa1-xWO4:Yb3+/Er3+(M=Li, Na,K) as crystal field dispensing and charge compensation ions on the up-conversionintensity and CIE chromaticity was studied via the Up-conversion emission spectra testand chromaticity calculation. When the doping ions are the same, the up-conversionluminescence intensities increase gradually with the increasing of Li+doping ratios, andthe CIE Chromaticity coordinates reaches the maximum offset when the doping ratiox=0.3; with the increasing of Na+doping ratios, the up-conversion luminescenceintensities firstly increases then remains at a certain level, the CIE Chromaticitycoordinates moving towards to longer wavelength along the CIE monochrometrajectory; with the increasing of K+doping ratios, the up-conversion luminescenceintensities increases firstly and then decreases, the CIE Chromaticity coordinatesfluctuate periodically in the vicinity540nm. When the dopants are distinctive, with theincreasing of the periodic numbers of alkali-metals, the up-conversion luminescenceintensities unchanged when the doping ratios x=0.2, and the intensities decreasesgradually when the doping ratios x=0.4; both the CIE Chromaticity coordinates of thedoping ratios, moving towards to short wavelength direction along the CIEmonochrome trajectory.Based on the power curve test and fluorescence lifetime test, the mechanism ofup-conversion luminescence of M0.4Ca0.8WO4:Yb3+/Er3+(M=Li, Na, K) was studied. Thetest result shows that the green up-conversion of the polycrystallines that dopingdifferent alkali-metal ions, are from the4S4Iand2H4Itransitions of Er3+, and the whole transition mechanism are two-photon processes; the redup-conversion of the polycrystallines are from the4F49/2I15/2transitions of Er3+, butthe transition mechanism are different, when the doped ions are Na+or K+ions, it is acoexistence processes of two-photon and single photo, when it is comes to Li+iondoping, the mechanism becomes single photo process on account of the saturatedup-conversion process that caused by the Li+ion doping. |
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