Authors: Chung Hsin Lu, Chien Hao Huang, Chung Tao Chen, Sheng Min Wang, Shu Jiuan Huang, Dorcas Zhang, Ramakant Kadam
Abstract: The photoluminescent properties of BaMgAl10O17: Eu2+ synthesized via a sol-gel process
employing citric acid (CA) and ethylene glycol (EG) were investigated in this study. The
photoluminescence intensity of Eu2+ emission increased with increase in the doping concentration
of Eu2+ up to 15 at %. The photoluminescence intensity of BaMgAl10O17: Eu2+ also varied with the
EG: CA ratio. SEM investigation indicates that the sol-gel derived particles exhibited an irregular
shape. The EPR studies showed that Eu2+ ions occupied the sites with non-cubic symmetry in the
prepared phosphors.
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Authors: Hyu Suk Kim, Hyug Jong Kim, Hyung Su Kim, Young Kyu Jeong, Suk Hwan Kim, Sang Woo Lee, Bong Kyo Jeong, Hyuoung Ho Lee, Byung Ho Choi
Abstract: An investigation is reported by coating BaMgAl10O17:Eu2+ phosphor by silicon oxide using
catalyzed atomic layer deposition. Nanoscaled SiO2 films were prepared at room temperature using
tetraethoxysilane (TEOS), H2O and NH3 as precursors, reactant gas and catalyst, respectively. AES
analysis showed the surface composition of coated phosphor was silicon oxide. In TEM and FE-SEM
analysis, the growth rate was about 0.7 Å/cycle and the surface morphology became smoother and
clearer than that of uncoated phosphor. The photoluminescence intensity (PL) increased up to 11.04%
as ALD cycle increased up to 200 ALD cycle. This means that the reactive surface of uncoated
phosphors is uniformly grown with stable silicon oxide to reduce the dead surface layer without
change of bulk properties. Moreover, it is found that nanoscaled SiO2 films are quite effective for the
improvement of the aging characteristics of photoluminescence.
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Authors: Hai Feng Li, Rong Zhou Gong, Xian Wang, Li Ren Fan, Gang He, Ming Zhong He, Ze Kun Feng
Abstract: M-type hexaferrites Ba(ZnZr)xFe12-2xO19 (x=0, 0.5, 1.0, 1.5) powders, have been synthesized by molten salt method, where x varies from 0 to 1.5 in steps of 0.5. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer(VSM) were used to analyze the structures and magnetic properties. The results showed that, the magnetoplumbite structures for all samples calcining at 1100°C have been formed. The magnetic hysteresis loop measurements of the hexagonal ferrites powders showed that the saturation magnetization (Ms), the remanent magnetization (Mr), and the coercitivity (Hc) of ferrites depend strongly on the chemical compositions of materials. The data showed that the max Hc was obtained when substitution of x=1.0 (Hc=63.9 Oe), while the best Ms was obtained when substitution of x=0.5 (Ms=54.02 emu/g). Zn and Zr substitutions greatly modified the magnetic properties of BaM hexaferrite.
2071
Authors: Li Jun Luo, Yi Wen Zhu, Ping Chen
Abstract: The phosphors SrAl2Si2O8 doped with different Eu2+ concentration were prepared by solid-state reaction technique, and their photoluminescent properties at different temperature were investigated. With the increase of Eu2+ content, two emission bands can be observed and this can be interpreted as Eu2+ ions occupying two types of sites in the crystal lattice. And their lifetime is decreasing, this result can be due to energy transfer among Eu2+ ions nonradiately at higher concentration of Eu2+ ions in the host lattices. The phosphor SrAl2Si2O8:0.40Eu shares intense blue emitting with broad excitation in the near-UV range. This phosphor may be an excellent blue phosphor for near ultraviolet InGaN-based white diodes.
956
Authors: Gilles Wallez, Arnold Lacanilao, Valérie Buissette, Thierry Le Mercier, Léo Mazerolles, Bertrand Pavageau, Laurent Servant
Abstract: The effects of various fluoride fluxes on the crystallization of blue phosphor BaMgAl10O17:Eu2+ were characterized using a wide panel of experimental methods. LiF appeared as the most efficient, with a significant increase of the photoluminescence yield under excitation at 280 nm. Besides, the recrystallization resulted in a redistribution of the dopant among the three crystallographic sites, leading to a strong increase of the excitation in the near-UV domain. This allowed the emission to increase by 40 % under a 400 nm irradiation, typically of interest for possible LED-blue phosphor systems. At last, the shaping into hexagonal single crystals allowed both a reduction of the thermal degradation under air, and the discovery of a novel regeneration process at moderate temperature.
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