固相合成法製備SrWO4：RE、M(RE=Pr、Dy，M=Na、K、Nb)及其光譜性質之研究

Abstract

A series of phosphors, Sr1-2x(RE,M)xWO4 and Sr1-xRExW1-xNbxO4 (x=0.005~0.1; RE=Pr3+, Dy3+; M=K+, Na+), were synthesized by the high temperature solid-state reaction, in order to develop a novel host material, SrWO4, which does not contain any rare-earth element. The effects on the luminescent properties of the optical center density (i.e. the RE concentration) and the charge compensation by K+, Na+ and Nb5+, as well as the influences of sintering temperature on the host crystal structure, were investigated by a series of techniques. X-ray diffraction confirmed that the phosphors sintered at 1100℃ were of a pure phase with the tetragonal Scheelite structure. The band gap of the host crystal was measured to be around 3.5 eV by the absorption spectra. For the Pr3+ doped phosphors, the photoluminescence spectra showed that under the excitation light of 448 nm, two main emissions at 487nm (blue, 3P0→3H4) and 647nm (red, 3P0→3F2) were observed. The two could be mixed to give out a white light with the CIE chromaticity coordinates located at (x=0.30, y=0.35). The optimum Pr3+ concentration was found to be 1.0 at.%. For the Dy3+ doped phosphors, a strong yellow emission at 574nm (4F9/2→6H13/2) and a weak blue emission at 486nm (4F9/2→6H15/2) were observed under the UV excitation of 351nm. The blend of the two emissions gave out a chartreuse light, corresponding to the CIE chromaticity coordinates of (x=0.39, y=0.43). The Dy3+ concentration for the maximum emission intensity was 3.0 at.%. The effects of the charge compensation ions were dependent on the type of the optical center. For Pr3+, the addition of K+ or Na+ was actually not beneficial, causing a deduction of both the emission intensity and the optimum doping concentration, whereas the addition of Nb5+ did increase the intensity of photoluminescence. In contrast, for Dy3+, doping of K+ or Na+ increased the photoluminescence intensity while Nb5+ caused a decrease of the intensity.