Using rare earth and zinc coordination polymers with aromatic carboxylic acids as the precursors, composing with the polyethylene glycol (PEG) as the dispersing media, micro crystalline phosphors Zn_3(PO_4)_2∶Eu 3+ a...Using rare earth and zinc coordination polymers with aromatic carboxylic acids as the precursors, composing with the polyethylene glycol (PEG) as the dispersing media, micro crystalline phosphors Zn_3(PO_4)_2∶Eu 3+ and LaPO_4∶Eu 3+ were synthesized by in-situ co-precipitation method. X-ray diffraction and scanning electronic micrograph were used to characterize the resultant samples, whose particle size are in the range of micrometer. The emission spectra of Zn_3(PO_4)_2∶Eu 3+ (λ_ ex=245 nm) and LaPO_4∶Eu 3+ (λ_ ex=390 nm) shows that the emission for Eu 3+ in Zn_3(PO_4)_2 is dominated by the 5D_0→7F_1 (592 nm) magnetic-dipole transition,While the dominant emission for Eu 3+ in LaPO_4 is the typical hypersensitive transition 5D_0→7F_2 (618 nm).展开更多
To provide preliminary information for design of rare earth phosphate-contained machinable ceramic, sintering and microstructure of LaPO_4 were investigated. The results show that LaPO_4 can be sintered independently ...To provide preliminary information for design of rare earth phosphate-contained machinable ceramic, sintering and microstructure of LaPO_4 were investigated. The results show that LaPO_4 can be sintered independently without other components from 1580 to 1620 ℃, and its grains are ellipsoidal or orbicular in surface but multilayer in the inside. The fracture of LaPO_4 ceramic presents transgranular along the larger grains and along-granular for the smaller grains. It is supposed that multi-layer structural LaPO_4 may contribute to machinabilities for those LaPO_4-contained ceramic duo to its low cleavage energy, which provides a easy path for cracks propagate of material removing, also leads crack deflections, branching and blunting helping to prevent macroscopic fractures from propagation beyond the local machining area.展开更多
Layer structured LaPO_4 was added to Al_2O_3 ceramic matrix to improve the machinability of the composites. Microstructures of the Al_2O_3/LaPO_4 ceramic composites were studied at various sintering temperatures (1450...Layer structured LaPO_4 was added to Al_2O_3 ceramic matrix to improve the machinability of the composites. Microstructures of the Al_2O_3/LaPO_4 ceramic composites were studied at various sintering temperatures (1450, 1520, 1580, 1700 ℃) and different LaPO_4 contents (pure Al_2O_3, 30% LaPO_4, 50% LaPO_4, 70% LaPO_4, pure LaPO_4). Microstructures of the Al_2O_3/LaPO_4 composites are largely dependent on the LaPO_4 content and sintering temperature. X-ray diffraction analysis shows that LaPO_4 phase would not exist in the Al_2O_3/LaPO_4 composites when sintered above 1700 ℃.展开更多
文摘Using rare earth and zinc coordination polymers with aromatic carboxylic acids as the precursors, composing with the polyethylene glycol (PEG) as the dispersing media, micro crystalline phosphors Zn_3(PO_4)_2∶Eu 3+ and LaPO_4∶Eu 3+ were synthesized by in-situ co-precipitation method. X-ray diffraction and scanning electronic micrograph were used to characterize the resultant samples, whose particle size are in the range of micrometer. The emission spectra of Zn_3(PO_4)_2∶Eu 3+ (λ_ ex=245 nm) and LaPO_4∶Eu 3+ (λ_ ex=390 nm) shows that the emission for Eu 3+ in Zn_3(PO_4)_2 is dominated by the 5D_0→7F_1 (592 nm) magnetic-dipole transition,While the dominant emission for Eu 3+ in LaPO_4 is the typical hypersensitive transition 5D_0→7F_2 (618 nm).
文摘To provide preliminary information for design of rare earth phosphate-contained machinable ceramic, sintering and microstructure of LaPO_4 were investigated. The results show that LaPO_4 can be sintered independently without other components from 1580 to 1620 ℃, and its grains are ellipsoidal or orbicular in surface but multilayer in the inside. The fracture of LaPO_4 ceramic presents transgranular along the larger grains and along-granular for the smaller grains. It is supposed that multi-layer structural LaPO_4 may contribute to machinabilities for those LaPO_4-contained ceramic duo to its low cleavage energy, which provides a easy path for cracks propagate of material removing, also leads crack deflections, branching and blunting helping to prevent macroscopic fractures from propagation beyond the local machining area.
文摘Layer structured LaPO_4 was added to Al_2O_3 ceramic matrix to improve the machinability of the composites. Microstructures of the Al_2O_3/LaPO_4 ceramic composites were studied at various sintering temperatures (1450, 1520, 1580, 1700 ℃) and different LaPO_4 contents (pure Al_2O_3, 30% LaPO_4, 50% LaPO_4, 70% LaPO_4, pure LaPO_4). Microstructures of the Al_2O_3/LaPO_4 composites are largely dependent on the LaPO_4 content and sintering temperature. X-ray diffraction analysis shows that LaPO_4 phase would not exist in the Al_2O_3/LaPO_4 composites when sintered above 1700 ℃.
