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Study on Preparation and Properties of Rare Earth Ions Cativated Y2O2S-based White Long-lasting Phosphor

Author: YangFan
Tutor: HuangPing
School: Taiyuan University of Technology
Course: Physical Electronics
Keywords: high temperature solid state reaction method white-lightlong-lasting phosphor Y2O2S rare earths ions
CLC: O482.31
Type: Master's thesis
Year: 2013
Downloads: 31
Quote: 0
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Abstract


Long-lasting phosphors are a special kind of photoluminescent materials, which can store the energy under excitation by ultraviolet light and visible light and can still light up for a long time after removal of the excitation source. They are widely used in several fields such as emergency lighting, road signs, safety indication, and decorative craft. At present, the colors of developed long-lasting phosphors cover most of the region from blue to red. However, the white-light long-lasting phosphors are still under investigation because the luminescence properties of the phosphors can not meet the application requirements.The white-light long-lasting phosphors Y2O2S:Tb3+, Sr2+, Zr4+were prepared through the high temperature solid state reaction method in this paper. The effect of calcination temperature and uniform temperature time on the phase and luminescent properties of the samples were characterized by the X-ray diffraction, photoluminescence and thermoluminescence spectra. The results show that the pure Y2O2S phase was obtained at1000℃for30min in reduced atmosphere. Under the288nm excitation, the blue light emission at417nm and the yellowish-green light emission at544nm originating from the5D3→7F5,5D4→7F5transitions of Tb3+respectively. The trap depth was0.64eV, the CIE chromaticity diagram was (0.24,0.33), and the decay time was160s (≥1mcd/m2) when the samples were synthesized at1000℃for30min in reduced atmosphere.In order to improve the luminescence properties of Y2O2S:Tb3+, Sr2+, Zr4+, the Eu3+ions doped Y2O2S:Tb3+, Sr2+, Zr4+white-light long-lasting phosphors were synthesized by the high temperature solid-state reaction method. The Y2O2S:Tb3+, Eu3+, Sr2+, Zr4+phosphors were characterized by the photoluminescence, long-lasting phosphorescence and thermoluminescence spectra. Under263nm UV excitation, the emission peaks at417nm and544nm were assigned to the5D3→7F5and5D4→7F5transitions of Tb3+respectively, and the emission peak at626nm was assigned to the5Do→-7F2transition of Eu3+. The white-light can be obtained by the appropriate mixing of them. With0.15%Eu3+concentration, the CIE chromaticity diagram was (0.28,0.31), the trap depth was0.89eV and the decay time could last for over220s (≥1mcd/m2).In order to improve the luminescence properties of Y2O2S:Tb3+,Eu3+,Sr2+,Zr4+, the Y2O2S:Tb3+,Eu3+,M2+,N4+white-light long-lasting phosphors doped with different tapys and number divalent and tetravalent ions were synthesized by the high temperature solid-state reaction method. The Y2O2S:Tb3+,Eu3+,M2+,N44+phosphors were characterized by the photoluminescence, long-lasting phosphorescence and thermoluminescence spectra. With different tapys and number divalent and tetravalent ions, the situation of emission peaks did not change. The sample with6%Mg2+and6%Si4+showed optimal initial luminance and afterglow time. The CIE chromaticity diagram was (0.29,0.30) and the decay time could last for over1400s (≥1mcd/m2).Under the above conditions, a series of novel Y2O2S:Dy3+, Mg2+, Si4+white-light long-lasting phosphors were synthesized by the high temperature solid-state reaction method. The Y2O2S:Dy3+, Mg2+, Si4+phosphors were characterized by X-ray diffraction, photoluminescence, long-lasting phosphorescence and thermoluminescence spectra. The samples doped with different concentration of Dy3+ions were composed of the pure Y2O2S phase. Under357nm UV excitation, the emission peaks at486nm and577nm were assigned to the4F9/2→6H15/2and4F9/2→6H13/2transitions of Dy3+respectively. When Dy3+concentration was1%, the CIE chromaticity diagram was (0.28,0.28), the trap depth was1.65eV and the decay time could last for over36min (≥1mcd/m2).

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CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Solid nature of the > Optical Properties > Luminescence
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