摻加稀土元素鋁酸釔螢光體之合成與特性鑑定

Abstract

本研究之主旨在於探討摻加稀土元素鋁酸釔螢光體之化學製程，與所摻加稀土元素之種類與濃度對此螢光體結構與發光性質之效應。高純度且結晶性極佳分別添加鈰、鐠、釹、釤、銪、釓、鋱、鏑、鈥、鉺、銩、鐿、鎦等鋁酸釔螢光體，係利用膠體共沈法於300℃與980℃分別燒結3小時與8小時所製得。我們亦探討製程中燒結溫度與燒結時間對螢光體純度之效應。X光繞射數據顯示：摻加稀土元素鋁酸釔系列螢光體晶格常數隨稀土離子半徑縮減而減小。同時，螢光體發光強度隨所摻加稀土離子濃度之增加先增加，達到一最高值後再下降。 為探討所添加活化劑釤離子濃度對鋁酸釔螢光發光光譜與顏色之效應，我們亦合成了一系列(Y3-xSmx)Al5O12 (0≦x≦1.0)螢光體，其晶格常數隨釤濃度增加而增加。然而，此系列螢光體之發射光譜，則隨釤濃度增加而減弱。 為了瞭解各螢光體色澤、混成特性與強度，我們也由光致發光光譜之量測所得數據，建立了(Y2.95R0.05)Al5O12與(Y3-xSmx)Al5O12等兩系列螢光體之色度座標。

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.