The Preparation And Surface Modification Of Rare Earth Fluoride Upconversion Luminescence Materials

Ytterbium(Ⅲ), erbium(Ⅲ) co-doped sodium yttrium fluoride (NaYF4:Er3+,Yb3+) powder are prepared by microemulsion method. CTAB(Cetyltrimethyl Ammonium Bromide), n-butyl alcohol, n-octane and water were selected as the microemulsion system. The influence of NaF/Y3+ratio, reaction temperature, reaction time, pH valve and aging time, heat treatment on phase formation, luminous efficiency and the particle size were studied. At last, the cubic samples were coated with TEOS and characterized.The result indicated that a-NaYF4:Yb3+,Er3+ samples were obtained at140℃for24h with the optimal pH value between5and6. And the β-NaYF4:Yb3+,Er3+samples were obtained at160℃for6Oh with the optimal pH value between1and4. The optimum annealing process is550℃for0.5hours.The samples showed a bright green light which the emission peak is541nm under the980nm LD exciting. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are utilized to analyze the phase, structure and size of the particles. The XRD pattern of a-NaYF4:Yb3+,Er3+ and β-NaYF4:Yb3+,Er3+ samples completely matched the PDF card No.77-2042(cubic NaYF4) and the PDF card No.28-1192(hexagonal NaYF4), respectively. The particle size of a-NaYF4:Yb3+,Er3+ and β-NaYF4:Yb3+,Er3+ is200nm and1 μm, respectively.