A novel yellowish green phosphor Tb3+ doped calcium molybdate (CaMoO4) was synthesized at 800 ℃ by conventional solid state reaction method and their crystal structure and luminescent properties were investigated. Th...A novel yellowish green phosphor Tb3+ doped calcium molybdate (CaMoO4) was synthesized at 800 ℃ by conventional solid state reaction method and their crystal structure and luminescent properties were investigated. The X-ray diffraction patterns (XRD) showed that they were simple crystalloid of CaMoO4∶Tb3+. Monitored at 550 nm, the excitation spectrum consisted of two bands and the two excitation peaks located at 305 and 380 nm respectively. The emission spectrum excited by 380 nm UV light was composed of four narrow bands. The strongest emission was located at 540 nm corresponding to 5D4-7F5 transition. The appropriate concentration of Tb3+ was 5%(mole fraction) for the highest emission intensity at 550 nm. These results showed that this Tb3+-activated CaMoO4 was a promising yellowish green phosphor for near-ultraviolet (NUV) InGaN-based white LED.展开更多
Eu-activated CaMoO_(4)phosphors were co-precipitated in an aqueous solution,and NH_(3)·H_(2)O,NH_(4)HCO_(3)and(NH_(2))_(2)CO as pre-cipitating aid agents were compared based on the morphology and particle size di...Eu-activated CaMoO_(4)phosphors were co-precipitated in an aqueous solution,and NH_(3)·H_(2)O,NH_(4)HCO_(3)and(NH_(2))_(2)CO as pre-cipitating aid agents were compared based on the morphology and particle size distribution of the phosphor samples.Sm3+as sensitizer ion was investigated on the luminescence of CaMoO_(4):Eu,and it could strengthen the 406 nm absorption of this phosphor.At last,the scheelite CaMoO_(4):Eu and wolframite ZnMoO_(4):Eu were selected to compare their host absorption.The result showed that the scheelite molybdate host exhibited stronger UV absorption than wolframite one.展开更多
Alkaline earth molybdate and tungstate thin films are widely prepared by electrochemical methods.In solutions,these crystals often grow into large clusters.Hence,it is difficult to obtain nanomolybdate and tungstate t...Alkaline earth molybdate and tungstate thin films are widely prepared by electrochemical methods.In solutions,these crystals often grow into large clusters.Hence,it is difficult to obtain nanomolybdate and tungstate thin films via electrodeposition.The morphologies of CaMoO_(4)thin films synthesized by galvanic cell route at different stages were compared and characterized.Scanning electron microscope(SEM)observations reveal that CaMoO_(4)thin films consist of two layers,sub-layer and top layer.Atomic force microscope(AFM)examination confirms that the roughness of sub-layer is within several nanometers.Both AFM analysis and the calculation based on XRD results favor that the average size of CaMoO_(4)crystallites is approximately several tens of nanometers.The top layer is usually rough due to large crystals in shapes of pyramids.Fluorescent study shows that the luminescence intensities of samples only with smooth layers are about four times of those filled with micrometer-sized CaMoO_(4)crystals.The reason accounting for the improvement of luminescent properties may lie in that there are much less lateral scattering for smooth samples.展开更多
基金supported by the National Natural Science Foundation of China(20963001)Natural Science Foundation of Guangxi Province,China(0575030,0832078)Innovation Project of Guangxi Graduate Education,China(2009106080817M364)~~
基金the Hebei Developing Foundation of Science &Technology (51215103b)
文摘A novel yellowish green phosphor Tb3+ doped calcium molybdate (CaMoO4) was synthesized at 800 ℃ by conventional solid state reaction method and their crystal structure and luminescent properties were investigated. The X-ray diffraction patterns (XRD) showed that they were simple crystalloid of CaMoO4∶Tb3+. Monitored at 550 nm, the excitation spectrum consisted of two bands and the two excitation peaks located at 305 and 380 nm respectively. The emission spectrum excited by 380 nm UV light was composed of four narrow bands. The strongest emission was located at 540 nm corresponding to 5D4-7F5 transition. The appropriate concentration of Tb3+ was 5%(mole fraction) for the highest emission intensity at 550 nm. These results showed that this Tb3+-activated CaMoO4 was a promising yellowish green phosphor for near-ultraviolet (NUV) InGaN-based white LED.
基金Project supported by the National Natural Science Foundation of China(50372086)the Minstry of Science and Technology of China(2006AA03A133)
文摘Eu-activated CaMoO_(4)phosphors were co-precipitated in an aqueous solution,and NH_(3)·H_(2)O,NH_(4)HCO_(3)and(NH_(2))_(2)CO as pre-cipitating aid agents were compared based on the morphology and particle size distribution of the phosphor samples.Sm3+as sensitizer ion was investigated on the luminescence of CaMoO_(4):Eu,and it could strengthen the 406 nm absorption of this phosphor.At last,the scheelite CaMoO_(4):Eu and wolframite ZnMoO_(4):Eu were selected to compare their host absorption.The result showed that the scheelite molybdate host exhibited stronger UV absorption than wolframite one.
基金financially supported by the National Natural Science Foundation of China (No.50802037)
文摘Alkaline earth molybdate and tungstate thin films are widely prepared by electrochemical methods.In solutions,these crystals often grow into large clusters.Hence,it is difficult to obtain nanomolybdate and tungstate thin films via electrodeposition.The morphologies of CaMoO_(4)thin films synthesized by galvanic cell route at different stages were compared and characterized.Scanning electron microscope(SEM)observations reveal that CaMoO_(4)thin films consist of two layers,sub-layer and top layer.Atomic force microscope(AFM)examination confirms that the roughness of sub-layer is within several nanometers.Both AFM analysis and the calculation based on XRD results favor that the average size of CaMoO_(4)crystallites is approximately several tens of nanometers.The top layer is usually rough due to large crystals in shapes of pyramids.Fluorescent study shows that the luminescence intensities of samples only with smooth layers are about four times of those filled with micrometer-sized CaMoO_(4)crystals.The reason accounting for the improvement of luminescent properties may lie in that there are much less lateral scattering for smooth samples.
