Nitrogen-rich Eu2+-doped Ca-α-SiAlON phosphors(Cam/2-xSi12-m-nAlm+nOnN16-n:xEu) were synthesized by a freeze-drying assisted combustion synthesis(CS) route. Fast-synthesized products with high purity and uniform part...Nitrogen-rich Eu2+-doped Ca-α-SiAlON phosphors(Cam/2-xSi12-m-nAlm+nOnN16-n:xEu) were synthesized by a freeze-drying assisted combustion synthesis(CS) route. Fast-synthesized products with high purity and uniform particle morphology were confirmed by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The analysis of lattice parameters by comparison with empirical equations showed that the as-prepared phosphors had low oxygen content. A series of samples were prepared according to the stoichiometry of Cam/2-0.08Si12-mAlmN16:0.08 Eu for further research. The influences of m value on the luminescence properties were investigated in detail. As m increased, a redshift phenomenon was observed in both the excitation and emission spectra. First-principle electronic structure calculations showed that the 3d energy level of Ca played an important role in the occurrence of the redshift phenomenon.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
Sm3＋-activated Y2028 red phosphors were prepared by the combustion method and microemulsion method at the first time. X-ray characterization and electron diffraction show that, Y202S：Sm3＋, Ti4＋, Mg2＋ samples prep...Sm3＋-activated Y2028 red phosphors were prepared by the combustion method and microemulsion method at the first time. X-ray characterization and electron diffraction show that, Y202S：Sm3＋, Ti4＋, Mg2＋ samples prepared by these two methods are pure hexagonal crystals in structure with a trivial change due to dopants. Scanning electron microscopy （SEM） results show that the product presents an almond-like sheet in uniform size. Under the excitation of 269 nm ultraviolet light, Y202S：Sm3＋ samples fabricated by these two methods exhibit three main groups of red emission lines located at 564, 604, and 656 nm, respectively, which are attributed to the transitions of 4G5/2 →6H5/2, 4G~/2 →6H7/2, 4G5/2 →6H9/2, respectively. The samples prepared by microemulsion are seven times higher in fluorescent emission intensity and half time longer in afterglow time than that prepared by combustion.展开更多
The Eu2+ doped red phosphor CaSrS2 was synthesized via the redox reaction of respective metal nitrates and sulfourea by combustion synthesis. A series of phosphor with different ration of sulfourea and the metallic ni...The Eu2+ doped red phosphor CaSrS2 was synthesized via the redox reaction of respective metal nitrates and sulfourea by combustion synthesis. A series of phosphor with different ration of sulfourea and the metallic nitrate were prepared and their luminescent properties were studied. The X-ray diffraction analysis (XRD) showed that they were pure crystalloid of CaSrS2, which belonged to cubic crystal structure. The scan electron microscope (SEM) patterns indicated that the size of CaSrS2 crystal would minish with the enhancing of the sulfourea quantity. The excitation spectra showed that there were a strong and two feebleness broad bands, which including two excitation peaks respectively. The emission spectrum was a broad band from 560～700 nm and the main peak located at 620 nm, which was a pure red light. The luminescent intensity of samples changed with the increasing of sulfourea and the intensity would reach the maximum when the sulfourea was 2.5 times of the theory dosage. This is beneficial to promote the performance of luminescence.展开更多
Using a simple combustion process, rare earth doped novel compounds like fluorides LiBF4 and Li3BF6 can be prepared. Combustion synthesis furnishes a quick method for preparation of these phosphors. The prepared phosp...Using a simple combustion process, rare earth doped novel compounds like fluorides LiBF4 and Li3BF6 can be prepared. Combustion synthesis furnishes a quick method for preparation of these phosphors. The prepared phosphors were characterized by the photoluminescence (PL) techniques. It is suggested that borofluoride based materials can be developed as low-cost phosphors. Formation of single phase compounds was confirmed by XRD. It is observed that prepared phosphors exhibited intense and characteristic Ce3+ and Eu2+ photoluminescence emission in blue visible region. This article summarizes fundamentals and possible applications of optically useful inorganic fluoride materials, with visible photoluminescence of Ce3+ and Eu2+ doped ions.展开更多
Cerium-doped yttrium aluminum garnet（YAG：Ce） as a yellow phosphor for white light-emitting diodes（LEDs） was synthesized via a facile combustion method using Y2 O3, CeO2, Al2 O3, Al,and NaClO4 as raw materials. Th...Cerium-doped yttrium aluminum garnet（YAG：Ce） as a yellow phosphor for white light-emitting diodes（LEDs） was synthesized via a facile combustion method using Y2 O3, CeO2, Al2 O3, Al,and NaClO4 as raw materials. The combustion synthesis approach utilizes the strong exothermic oxidation of aluminum to realize a self-sustaining reaction. In this study, we investigated the effects of the ratios of Al2 O3 to AI,fluxes, and coprecipitated materials as raw materials on the luminescence properties of the synthesized YAG：Ce phosphors. When the amount of Al2 O3 x is varied, the combustion reaction proceeds at x ≤ 1.8,with x = 1.725 being the optimum condition for producing a high-performance product. When 5 wt%BaF2 is added, the luminescence intensity is significantly improved owing to a decrease of YAP（YAlO3）formation with improved uniformity. However, the addition of CaF2 and NaF does not improve the luminescence properties. To suppress the segregation of CeO2, we used the coprecipitated material Y2 O3-CeO2 as a raw material. Unlike with separate addition of Y2 O3 and CeO2, Ce ions are uniformly distributed in the coprecipitated material, resulting in improved luminescence properties. The combination of BaF2 and coprecipitated material significantly improves the internal quantum efficiency to83.0%, which is close to that of commercial phosphors.展开更多
The preparation of NaCaPO4 doped with rare earth （RE） ions Ce3＋, Eu3＋ and Dy3＋ by combustion method was described. Under UV excitation （251 nm） of NaCaPO4：Ce3＋ showsd emission （367 nm） in UV range. When NaC...The preparation of NaCaPO4 doped with rare earth （RE） ions Ce3＋, Eu3＋ and Dy3＋ by combustion method was described. Under UV excitation （251 nm） of NaCaPO4：Ce3＋ showsd emission （367 nm） in UV range. When NaCaPO4：Dy3＋ phosphor was excited at 349 nm, the emission spectrum showed intense bands at 482 nm （blue） and 576 nm （yellow）. In Eu activated NaCaPO4 phosphor, the emission spectrum showed a dominant peak at 594 nm （orange） while others were at 614 and 621 nm （red） when excited at 393 nm. The prepared phosphor was characterized by X-ray diffraction （XRD）, scanning electron microscope （SEM） and photoluminescence （PL） measurement. Thus, the photoluminescence behavior of NaCaPO4：Ce3＋ was strongly suggested for scintillator. Likewise, Eu3＋ and Dy3＋ activated NaCaPO4 phosphors were recommended for near-UV white light-emitting diodes （LEDs）.展开更多
This paper reports the comparative investigations of the structural and spectral properties of Y3Al5O12∶Eu3+ (YAG∶Eu) and Y3Al5O12∶Eu3+,Si4+ (YAG∶Eu,Si) phosphors synthesized by combustion method at low temperatur...This paper reports the comparative investigations of the structural and spectral properties of Y3Al5O12∶Eu3+ (YAG∶Eu) and Y3Al5O12∶Eu3+,Si4+ (YAG∶Eu,Si) phosphors synthesized by combustion method at low temperature.A pure phase was identified for the YAG∶Eu phosphor with a suitable amount of SiO2.Rietveld refinement and analytical calculation of different structural parameters were performed to get the idea about the SiO2 substitution in YAG∶Eu.The characteristic red luminescence corresponding to Eu3+ transitions was observed after irradiation with ultra violet (UV) light and enhanced with SiO2 addition.Jorgensen formula and nephelauxetic ratio were used to understand the ligand behavior of Eu-O bond in YAG doped phosphor.The Judd-Ofelt intensity parameters and color properties of the phosphors were determined in detail.An efficient synthesis method for YAG∶Eu phosphor,compatible for industrial applications,was proposed.展开更多
基金This work was financially supported by the Chinese Academy of Sciences(CAS)Interdisciplinary Innovation Teamthe Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China(No.19XNLG13).
文摘Nitrogen-rich Eu2+-doped Ca-α-SiAlON phosphors(Cam/2-xSi12-m-nAlm+nOnN16-n:xEu) were synthesized by a freeze-drying assisted combustion synthesis(CS) route. Fast-synthesized products with high purity and uniform particle morphology were confirmed by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The analysis of lattice parameters by comparison with empirical equations showed that the as-prepared phosphors had low oxygen content. A series of samples were prepared according to the stoichiometry of Cam/2-0.08Si12-mAlmN16:0.08 Eu for further research. The influences of m value on the luminescence properties were investigated in detail. As m increased, a redshift phenomenon was observed in both the excitation and emission spectra. First-principle electronic structure calculations showed that the 3d energy level of Ca played an important role in the occurrence of the redshift phenomenon.
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financially supported by the Basic Theory Research Fund of Research Institute of Metallurgy Engineering,University of Science and Technology Beijing(No.YJ2012-009)
文摘Sm3＋-activated Y2028 red phosphors were prepared by the combustion method and microemulsion method at the first time. X-ray characterization and electron diffraction show that, Y202S：Sm3＋, Ti4＋, Mg2＋ samples prepared by these two methods are pure hexagonal crystals in structure with a trivial change due to dopants. Scanning electron microscopy （SEM） results show that the product presents an almond-like sheet in uniform size. Under the excitation of 269 nm ultraviolet light, Y202S：Sm3＋ samples fabricated by these two methods exhibit three main groups of red emission lines located at 564, 604, and 656 nm, respectively, which are attributed to the transitions of 4G5/2 →6H5/2, 4G~/2 →6H7/2, 4G5/2 →6H9/2, respectively. The samples prepared by microemulsion are seven times higher in fluorescent emission intensity and half time longer in afterglow time than that prepared by combustion.
基金the Hebei Developing Foundation of Science &Technology (51215103b)
文摘The Eu2+ doped red phosphor CaSrS2 was synthesized via the redox reaction of respective metal nitrates and sulfourea by combustion synthesis. A series of phosphor with different ration of sulfourea and the metallic nitrate were prepared and their luminescent properties were studied. The X-ray diffraction analysis (XRD) showed that they were pure crystalloid of CaSrS2, which belonged to cubic crystal structure. The scan electron microscope (SEM) patterns indicated that the size of CaSrS2 crystal would minish with the enhancing of the sulfourea quantity. The excitation spectra showed that there were a strong and two feebleness broad bands, which including two excitation peaks respectively. The emission spectrum was a broad band from 560～700 nm and the main peak located at 620 nm, which was a pure red light. The luminescent intensity of samples changed with the increasing of sulfourea and the intensity would reach the maximum when the sulfourea was 2.5 times of the theory dosage. This is beneficial to promote the performance of luminescence.
文摘Using a simple combustion process, rare earth doped novel compounds like fluorides LiBF4 and Li3BF6 can be prepared. Combustion synthesis furnishes a quick method for preparation of these phosphors. The prepared phosphors were characterized by the photoluminescence (PL) techniques. It is suggested that borofluoride based materials can be developed as low-cost phosphors. Formation of single phase compounds was confirmed by XRD. It is observed that prepared phosphors exhibited intense and characteristic Ce3+ and Eu2+ photoluminescence emission in blue visible region. This article summarizes fundamentals and possible applications of optically useful inorganic fluoride materials, with visible photoluminescence of Ce3+ and Eu2+ doped ions.
基金supported by the"Nanotechnology Platform"Program of the Ministry of Education,Culture,Sports,Science and Technology of Japan(MEXT)
文摘Cerium-doped yttrium aluminum garnet（YAG：Ce） as a yellow phosphor for white light-emitting diodes（LEDs） was synthesized via a facile combustion method using Y2 O3, CeO2, Al2 O3, Al,and NaClO4 as raw materials. The combustion synthesis approach utilizes the strong exothermic oxidation of aluminum to realize a self-sustaining reaction. In this study, we investigated the effects of the ratios of Al2 O3 to AI,fluxes, and coprecipitated materials as raw materials on the luminescence properties of the synthesized YAG：Ce phosphors. When the amount of Al2 O3 x is varied, the combustion reaction proceeds at x ≤ 1.8,with x = 1.725 being the optimum condition for producing a high-performance product. When 5 wt%BaF2 is added, the luminescence intensity is significantly improved owing to a decrease of YAP（YAlO3）formation with improved uniformity. However, the addition of CaF2 and NaF does not improve the luminescence properties. To suppress the segregation of CeO2, we used the coprecipitated material Y2 O3-CeO2 as a raw material. Unlike with separate addition of Y2 O3 and CeO2, Ce ions are uniformly distributed in the coprecipitated material, resulting in improved luminescence properties. The combination of BaF2 and coprecipitated material significantly improves the internal quantum efficiency to83.0%, which is close to that of commercial phosphors.
基金Project supported by University Grant Commission (UGC), New Delhi, India
文摘The preparation of NaCaPO4 doped with rare earth （RE） ions Ce3＋, Eu3＋ and Dy3＋ by combustion method was described. Under UV excitation （251 nm） of NaCaPO4：Ce3＋ showsd emission （367 nm） in UV range. When NaCaPO4：Dy3＋ phosphor was excited at 349 nm, the emission spectrum showed intense bands at 482 nm （blue） and 576 nm （yellow）. In Eu activated NaCaPO4 phosphor, the emission spectrum showed a dominant peak at 594 nm （orange） while others were at 614 and 621 nm （red） when excited at 393 nm. The prepared phosphor was characterized by X-ray diffraction （XRD）, scanning electron microscope （SEM） and photoluminescence （PL） measurement. Thus, the photoluminescence behavior of NaCaPO4：Ce3＋ was strongly suggested for scintillator. Likewise, Eu3＋ and Dy3＋ activated NaCaPO4 phosphors were recommended for near-UV white light-emitting diodes （LEDs）.
文摘This paper reports the comparative investigations of the structural and spectral properties of Y3Al5O12∶Eu3+ (YAG∶Eu) and Y3Al5O12∶Eu3+,Si4+ (YAG∶Eu,Si) phosphors synthesized by combustion method at low temperature.A pure phase was identified for the YAG∶Eu phosphor with a suitable amount of SiO2.Rietveld refinement and analytical calculation of different structural parameters were performed to get the idea about the SiO2 substitution in YAG∶Eu.The characteristic red luminescence corresponding to Eu3+ transitions was observed after irradiation with ultra violet (UV) light and enhanced with SiO2 addition.Jorgensen formula and nephelauxetic ratio were used to understand the ligand behavior of Eu-O bond in YAG doped phosphor.The Judd-Ofelt intensity parameters and color properties of the phosphors were determined in detail.An efficient synthesis method for YAG∶Eu phosphor,compatible for industrial applications,was proposed.
