The Influence of Processing Parameters on Photoluminescent Properties of Ba 2 ZnS 3 :Mn Phosphors by Double-Crucible Met
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L9.9.1
The Influence of Processing Parameters on Photoluminescent Properties of Ba2ZnS3:Mn Phosphors by Double-Crucible Method Yu-Feng Lin, Yen-Hwei Chang and Bin-Siang Tsai Department of Materials Science and Engineering, National Cheng Kung University, Tainan, 701 Taiwan, ROC
ABSTRACT Red light emitting of Mn2+ doped Ba2ZnS3 phosphor powders have been synthesized by double-crucible method at different thermal treatments. XRD results indicate that the raw materials are completely sulfurized above 950oC, and the Ba2ZnS3: Mn2+ powders don’t change its orthorhombic crystal structure with increasing doping concentration from 0 to 0.8 mol%. The photoluminescence of Ba2ZnS3: Mn2+ powders fulfilled the most efficient emission at the excitation wavelength λex=358 nm and showed the red emission light with peak wavelength λem=627nm at the doping concentration of Mn2+ ion between 0.2 and 0.8 mol%. The high-luminance red emission results from the 4T1 (4G)－6A1 (6S) transition in the Mn2+ ion. Ba2ZnS3: Mn2+ phosphors synthesized by double-crucible method have broad emission spectra (550nm~750nm) with FWHM (full width at half maximum broadband) about 66nm. In our research, the Ba2ZnS3 doped with 0.4 mol% Mn2+ has the highest luminescent intensity as thermal treatment at 950oC for 16 hours and the CIE coordinate is x=0.66, y=0.33.
INTRODUCTION Transition metal ions doped wide band gap Ⅱ-Ⅵ compounds such as the zinc chalcogenide ZnS [1-3] and the alkaline-earth chalcogenides (AES) MgS [4-6], CaS [7-9], SrS [10-12] and BaS [6,13-14] are known to be efficient luminescent materials for the realization of multicolor electroluminescent and cathodoluminescent devices. The 3d transition metal ions utilized in commercial powder phosphors have three electrons (in the case of Cr3+ and Mn4+) or five electrons (Mn2+ and Fe3+) occupying the outermost 3d electron orbitals of the ions. When the 3d ions are incorporated into liquids or solids, spectroscopic properties are considerably changed from those of gaseous free ions. There is considerable interest in Mn-doped wide band gap phosphor materials – ZnS:Mn for example. The high efficiency of ZnS:Mn2+ has motivated efforts to shift or broaden the yellow 4T1(4G)Æ6A1(6S) emission of Mn2+ to achieve a wider range of colors for phosphor or filtered white light displays. Hence several Ⅱ-Ⅵ mixed sulfides doped with rare-earth metal ions or transition metal ions have been investigated: Ca1-xSrxS: Ce [15], Ca1-xSrxS: Eu [16], Zn1-xSrxS: Ce [17], Zn1-xMgxS: Mn [18-19]. To date, barium zinc sulfide was fist prepared by Hoppe [20] by firing zinc oxide and barium oxide in an atmosphere of hydrogen sulfide (H2S). Subsequently, the solubility of ZnS in BaS has been studied by Megson [21]. It is discovered that the firing of BaS and ZnS (in the molar quantities 2BaS:1ZnS) in an oxygen-free nitrogen atmosphere produced the barium zinc sulfide (Ba2ZnS3). The role of the transition metal ion Mn2+ doped in barium zinc sulfide has not been completely investigated yet.
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In this work, we have synthesized t
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