BaAl2S4∶Eu2+ nanoparticles with a size distribution of 50—150 nm were prepared by the sol-gel method. The particles were near spherical and had an intensive green emission when they were excited at 254 nm, after cal...BaAl2S4∶Eu2+ nanoparticles with a size distribution of 50—150 nm were prepared by the sol-gel method. The particles were near spherical and had an intensive green emission when they were excited at 254 nm, after calcining at 1000 ℃ in a mixture of H2S(volume fraction 10%)+N2(volume fraction 90%) for 1.5 h. X-ray diffraction patterns indicate that BaAl2S4∶Eu2+ has a cubic structure. The emission and excitation spectra show that emission was from the 4f65d4f7 transition of the activated Eu2+. The highest photoluminescence(PL) luminance is 420 cd/m2. This study indicate that the BaAl2S4∶Eu2+ could be used as photoluminescent nanocomposite materials.展开更多
The optical properties of blue emitting BaAl2S4:Eu thin-films were studied. The emission peak is around 470 nm, whose FWHM (full width at half maximum) is 35 nm. The dielectric constant is 3.03 from transmission spect...The optical properties of blue emitting BaAl2S4:Eu thin-films were studied. The emission peak is around 470 nm, whose FWHM (full width at half maximum) is 35 nm. The dielectric constant is 3.03 from transmission spectrum, and the optical band gap is approximately 4.6 eV. It is found that the cubic phase and orthorhombic phase exist in fabricated thin-films. Furthermore, the energy band structure of BaAl2S4 : Eu thin-films from X-ray photo-electron spectra (XPS) and the absorption spectra were analyzed.展开更多
Blue-green luminescent BaAl2O4：Eu2＋,Dy3＋ phosphor powders were synthesized via combustion synthesis method assisted by microwave irradiation in air. The phosphors were characterized by X-ray diffraction （XRD）, sc...Blue-green luminescent BaAl2O4：Eu2＋,Dy3＋ phosphor powders were synthesized via combustion synthesis method assisted by microwave irradiation in air. The phosphors were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and fluorescence spectrophotometer. The XRD results revealed that when the concentration of urea was over 3 times higher than theoretical quantities, a BaAl2O4 single hexagonal phase was obtained. The SEM results revealed that the surface of the BaAl2O4：Eu2＋,Dy3＋ powder samples showed lots of voids and pores. The BaAl2O4：Eu2＋,Dy3＋ phosphors exhibited a broad emission band of main peak at 496 nm and a shoulder peak at 426 nm under excitation of 337 nm. The BaAl2O4：Eu2＋,Dy3＋ phosphors at the Eu2＋ concentration of 1 mol.% showed the strongest luminescent intensity. Long afterglow phosphorescence was observed in the dark with naked eyes after the removal of the excitation source.展开更多
The blue-green emitting Eu2＋ and Nd3＋ doped polycrystalline barium aluminate （BaAI204：Eu2＋,Nd3＋） phosphor, was prepared by a solution-combustion method at 500 ℃without a post-annealing process. The characteris...The blue-green emitting Eu2＋ and Nd3＋ doped polycrystalline barium aluminate （BaAI204：Eu2＋,Nd3＋） phosphor, was prepared by a solution-combustion method at 500 ℃without a post-annealing process. The characteristic variation in the structural and luminescence properties of the as-prepared samples was evaluated with regards to a change in the Ba/A1 molar ratio from 0.1：1 to 1.4：1. The morphologies and the phase structures of the products were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）, while the optical properties were investigated using ultra-violet （UV） and photoluminescence （PL） spectroscopy, respectively. The XRD and TEM results revealed that the average crystallite size of the BaAl2O4：Eu2＋,Nd3＋ phosphor was about 70 urn. The broad-band UV-excited luminescence of the phosphors was observed at 2max=500 um due to transitions from the 4f^65d1 to the 4f7 configuration of the Eu2＋ ion. The PL results indicated that the main peaks in the emission and excitation spectrum of phosphor particles slightly shifted to the short wavelength due to the changes in the crystal field due to the structure changes caused by the variation in the quantity of the Ba ions in the host lattice.展开更多
文摘BaAl2S4∶Eu2+ nanoparticles with a size distribution of 50—150 nm were prepared by the sol-gel method. The particles were near spherical and had an intensive green emission when they were excited at 254 nm, after calcining at 1000 ℃ in a mixture of H2S(volume fraction 10%)+N2(volume fraction 90%) for 1.5 h. X-ray diffraction patterns indicate that BaAl2S4∶Eu2+ has a cubic structure. The emission and excitation spectra show that emission was from the 4f65d4f7 transition of the activated Eu2+. The highest photoluminescence(PL) luminance is 420 cd/m2. This study indicate that the BaAl2S4∶Eu2+ could be used as photoluminescent nanocomposite materials.
文摘The optical properties of blue emitting BaAl2S4:Eu thin-films were studied. The emission peak is around 470 nm, whose FWHM (full width at half maximum) is 35 nm. The dielectric constant is 3.03 from transmission spectrum, and the optical band gap is approximately 4.6 eV. It is found that the cubic phase and orthorhombic phase exist in fabricated thin-films. Furthermore, the energy band structure of BaAl2S4 : Eu thin-films from X-ray photo-electron spectra (XPS) and the absorption spectra were analyzed.
基金supported by the National Natural Science Foundation of China (60477034)
文摘Blue-green luminescent BaAl2O4：Eu2＋,Dy3＋ phosphor powders were synthesized via combustion synthesis method assisted by microwave irradiation in air. The phosphors were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and fluorescence spectrophotometer. The XRD results revealed that when the concentration of urea was over 3 times higher than theoretical quantities, a BaAl2O4 single hexagonal phase was obtained. The SEM results revealed that the surface of the BaAl2O4：Eu2＋,Dy3＋ powder samples showed lots of voids and pores. The BaAl2O4：Eu2＋,Dy3＋ phosphors exhibited a broad emission band of main peak at 496 nm and a shoulder peak at 426 nm under excitation of 337 nm. The BaAl2O4：Eu2＋,Dy3＋ phosphors at the Eu2＋ concentration of 1 mol.% showed the strongest luminescent intensity. Long afterglow phosphorescence was observed in the dark with naked eyes after the removal of the excitation source.
基金Project supported by South African National Research Foundation(NRF)
文摘The blue-green emitting Eu2＋ and Nd3＋ doped polycrystalline barium aluminate （BaAI204：Eu2＋,Nd3＋） phosphor, was prepared by a solution-combustion method at 500 ℃without a post-annealing process. The characteristic variation in the structural and luminescence properties of the as-prepared samples was evaluated with regards to a change in the Ba/A1 molar ratio from 0.1：1 to 1.4：1. The morphologies and the phase structures of the products were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）, while the optical properties were investigated using ultra-violet （UV） and photoluminescence （PL） spectroscopy, respectively. The XRD and TEM results revealed that the average crystallite size of the BaAl2O4：Eu2＋,Nd3＋ phosphor was about 70 urn. The broad-band UV-excited luminescence of the phosphors was observed at 2max=500 um due to transitions from the 4f^65d1 to the 4f7 configuration of the Eu2＋ ion. The PL results indicated that the main peaks in the emission and excitation spectrum of phosphor particles slightly shifted to the short wavelength due to the changes in the crystal field due to the structure changes caused by the variation in the quantity of the Ba ions in the host lattice.
