| Summary: | 碩士 === 國立交通大學 === 應用化學研究所 === 85 === This research is attempted to investigate the chemical synthesis and the effects of quantity and types of rare-earth activator (R3+) doping on the structural and luminescent properties of the Y3Al5O12(YAG) phosphors. Well crystalline and x-ray pure powers of R-doped (R=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) YAG were synthesized by heat treatment of gel-precipitated precursors, first at 300℃ for 3 hours and then at 980℃ for 8 hours. The effects of sntering time and temperature on the purity of R-doped YAG was also investigated to determine the optimal preparation conditions. Cell parameters of R-doped YAG phases as a function of R3+ size were found to decrease, in general, as the atomic number of R increased due to lanthanide contraction, as indicated by x-ray diffraction data. The intensity of luminescent emission for R-doped YAG phase was found to first increase with increasing activator R concentration (i.e., x), then reach a maximum and finally decrease as x further increases. In order to investigate the concentration effect of Sm activator on the spectral properties and color characteristics, we have also prepared a series of (Y3-xSmx)Al5O12 phases with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, respectively. The cell parameters (a0) of Sm-doped YAG as a function of activator concentration x were discovered to increase with increasing x. This observation was attributed to the larger size of Sm3+ compared to that of Y3+. On the contrary, the intensity of emission spectra of Sm-doped YAG was found to decrease with increasing x. To understand the boundaries of color mixing and compare colors with different intensity values, we have also established CIE chromaticity diagrams for two series of (Y2.95R0.05)Al5O12 and (Y3-xSmx)Al5O12 phosphors, based on the data extracted from photoluminescent emission and excitation spectra.
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