The sulfate ions modified YAG：Ce^（3＋） phosphors were prepared by co-precipitation method and characterized by X-ray diffraction,transmission electron microscopy,and photoluminescence.Effects of sulfate ions on the...The sulfate ions modified YAG：Ce^（3＋） phosphors were prepared by co-precipitation method and characterized by X-ray diffraction,transmission electron microscopy,and photoluminescence.Effects of sulfate ions on the photoluminescence（PL） property of the as-prepared YAG：Ce^（3＋） phosphors were studied,with sodium dodecyl sulfate（SDS） being added to R^（3＋）（Ce^（3＋）,Y^（3＋）,Al^（3＋）） ions.Results indicated that pure YAG：Ce^（3＋） phosphors with different ratios of sulfate ions could be easily obtained by calcining the as-synthesized precursor at 950 ℃ for 2 h,the YAG：Ce^（3＋） phosphors with an optimal mass ratio of 3.5 wt.%SDS had the highest emission intensity and the best dispersion behavior,and the fluorescence decay of the as-obtained YAG：Ce^（3＋） phosphors was related to the lattice defect,reabsorption and cross correlation.Furthermore,thermal quenching properties of the YAG：Ce^（3＋） phosphors and the YAG：Ce^（3＋） phosphors with 3.5 wt.%SDS were also discussed,indicating that the YAG：Ce^（3＋） with SDS phosphors could have potential applications in the daylight LEDs or warm white LEDs.展开更多
In order to confirm the relationship between the luminescence and the ratio of Ce3+/Ce4+ more clearly, a series of YAG:Ce3+ (Yttrium Aluminum Garnet, Y2.94Al5O12:0.06Ce3+) phosphors were pre- pared under different sin...In order to confirm the relationship between the luminescence and the ratio of Ce3+/Ce4+ more clearly, a series of YAG:Ce3+ (Yttrium Aluminum Garnet, Y2.94Al5O12:0.06Ce3+) phosphors were pre- pared under different sintering atmosphere. A semi-quantitative analysis based on X-ray photoe-lectron spectroscopy (XPS) was introduced to study the mole ratio of Ce3+/Ce4+ in the as-synthesized YAG:Ce3+ phosphors. The results indicated that the percentage of Ce3+/(Ce3+ + Ce4+) reached 88.46% under the reduction atmosphere. The emission intensity of YAG:Ce3+ phosphors was in-creased significantly with the increasing of Ce3+ concentration.展开更多
A Matlab （2009a） program was developed to simulate the photons emitted by the LED chips. The photons＇ transmission, reflection, and refraction in phosphor layers with different shapes were calculated in this progra...A Matlab （2009a） program was developed to simulate the photons emitted by the LED chips. The photons＇ transmission, reflection, and refraction in phosphor layers with different shapes were calculated in this program. The CCT was calculated at different emergent angles with different layer profiles, such as planar layer, hemispherical layer （with different diameters）, half ellipsoid layer and other irregular shapes. As a consequence of optimization of angular color uniformity, the trend of configuration of the phosphor layer was discussed and analyzed.展开更多
YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some interm...YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG ： Ce^3 ＋ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG：Ce^3 ＋.展开更多
基金supported by the Research Fund for Doctoral Program of Higher Education of China(20120201130004)the Science and Technology Developing Project of Shaanxi Province(2015KW-001)+1 种基金the National Natural Science Foundation of China(61078058)Partially by the National Natural Science Foundation of China Major Research Plan on Nanomanufacturing(91323303)
文摘The sulfate ions modified YAG：Ce^（3＋） phosphors were prepared by co-precipitation method and characterized by X-ray diffraction,transmission electron microscopy,and photoluminescence.Effects of sulfate ions on the photoluminescence（PL） property of the as-prepared YAG：Ce^（3＋） phosphors were studied,with sodium dodecyl sulfate（SDS） being added to R^（3＋）（Ce^（3＋）,Y^（3＋）,Al^（3＋）） ions.Results indicated that pure YAG：Ce^（3＋） phosphors with different ratios of sulfate ions could be easily obtained by calcining the as-synthesized precursor at 950 ℃ for 2 h,the YAG：Ce^（3＋） phosphors with an optimal mass ratio of 3.5 wt.%SDS had the highest emission intensity and the best dispersion behavior,and the fluorescence decay of the as-obtained YAG：Ce^（3＋） phosphors was related to the lattice defect,reabsorption and cross correlation.Furthermore,thermal quenching properties of the YAG：Ce^（3＋） phosphors and the YAG：Ce^（3＋） phosphors with 3.5 wt.%SDS were also discussed,indicating that the YAG：Ce^（3＋） with SDS phosphors could have potential applications in the daylight LEDs or warm white LEDs.
文摘In order to confirm the relationship between the luminescence and the ratio of Ce3+/Ce4+ more clearly, a series of YAG:Ce3+ (Yttrium Aluminum Garnet, Y2.94Al5O12:0.06Ce3+) phosphors were pre- pared under different sintering atmosphere. A semi-quantitative analysis based on X-ray photoe-lectron spectroscopy (XPS) was introduced to study the mole ratio of Ce3+/Ce4+ in the as-synthesized YAG:Ce3+ phosphors. The results indicated that the percentage of Ce3+/(Ce3+ + Ce4+) reached 88.46% under the reduction atmosphere. The emission intensity of YAG:Ce3+ phosphors was in-creased significantly with the increasing of Ce3+ concentration.
文摘A Matlab （2009a） program was developed to simulate the photons emitted by the LED chips. The photons＇ transmission, reflection, and refraction in phosphor layers with different shapes were calculated in this program. The CCT was calculated at different emergent angles with different layer profiles, such as planar layer, hemispherical layer （with different diameters）, half ellipsoid layer and other irregular shapes. As a consequence of optimization of angular color uniformity, the trend of configuration of the phosphor layer was discussed and analyzed.
文摘YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG ： Ce^3 ＋ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG：Ce^3 ＋.
