| Summary: | 碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 98 === YTiNbO6:RE(RE=Dy、Er、Pr) and YTiNbO6:(Dy,Ta) phosphors were synthesized by solid state reaction in this work. The effects of rare earth ion concentration, distortion of host, sintering temperature, and the grain size, and morphology on the photoluminescent properties were investigated and optimized.
YTiNbO6:RE compounds of the Euxenite structure (PDF no.83.1318) were successfully synthesized by sintering at 1300℃. The fundamental absorption edge was calculated from the absorption spectra to be at 339.7nm, corresponding to the band-gap energy of 3.65eV. Under the excitation wavelength of 353nm, the dominant emission clusters were located around 482nm and 579nm, arising from the Dy3+ transitions 4F9/2→6H15/2 and 4F9/2→6H13/2 in YTiNbO6:Dy. The optimum doping level of Dy3+ in YTiNbO6:Dy was found to be 5mol%. The CIE chromaticity coordinate was at (0.31,0.37) for YTiNbO6:Dy, corresponding to a color tone of near-white. Under the charge-transfer excitation at 290nm, a broad emission at 400~670nm was observed in addition to the sharp lines from the Dy3+ transitions. This broad emission is thought to come from the NbO6 group of the host. When Nb was substituted by Ta, the road emission was increased with the Ta concentration and reached maxima for the pure Ta compound, i.e. YTiTaO6:Dy, indicating that TaO6 emits more efficient than NbO6 at this wavelength region.
The optical spectra of YTiNbO6:Er is dominated by the strong emission centered at 558nm. The optimum concentration for Er3+ was found to be 10 mol%. The CIE (x,y) coordinate of YTiNbO6:Er was calculated to be at (0.29,0.67), corresponding to the color tone of yellowish green. The optical spectra of YTiNbO6:Pr were characterized by a strong emission at the 615 nm, which came from the Pr3+ 1D2→3H4 and 3P0→3H6 transitions. The optimum concentration for Pr3+ was determined to be 0.5 mol%, and the (x,y) coordinate was at (0.67,0.33), having the red color.
Keyword: phosphor, euxenite structure
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