Preparation And Characterization Of Upconversion Fluorides Nanometer Materials

The history of upconversion luminescence,recent progress and future prospect were reviewed in the dissertation. Nanoupconversion luminescence materials of BaF2:Yb³⁺,Er³⁺,LaF3:Yb³⁺,Er³⁺andYF3:Yb³⁺,Er³⁺were prepared from the quaternary microemulsions of CTAB, n-butanol, n-octane and water or brine solution. The X-ray diffraction (XRD) patterns were indexed to pure BaF2,LaF3 and YF3 phases. The diameter of the particales, calculated with the help of Debye-Scherrer equation, revealed that these particales were nanoparticals;Environment scanning electron microscopy(ESEM) images showed spherical BaF2:Yb³⁺,Er³⁺,LaF3:Yb³⁺,Er³⁺andYF3:Yb³⁺,Er³⁺nanoparticles were about 13～30 nm in diameter.The fluorescence emission band of nanoparticles peaked at about 1540 nm (4I13/2→4I15/2).At room temperature,by using 980nm laser to excited these three kinds of samples, the red and green light can be observed.The influences that ratios Yb³⁺ ions to Er³⁺ ions on the upconversion luminescent intensity were discussed.The dependences of pump power on luminescent intensity were investigated so as to determine both red emission and green emission are the absorption process of double-photon,and the mechanisms of the upconversion luminescence were also discussed.