Papers by Keyword: Phosphor

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Authors: Y. Kawai, Tomohiko Maeda, Yoshihiro Nakamura, Yoji Sakurai, Motoaki Iwaya, Satoshi Kamiyama, Hiroshi Amano, Isamu Akasaki, Masahiro Yoshimoto, Tomoaki Furusho, Hiroyuki Kinoshita, Hiromu Shiomi
Abstract: We demonstrate high-speed and high-quality 6H-SiC homoepitaxial growth on a 1°-off c-plane SiC substrate by a closed-space sublimation method. By optimizing the size of single-crystal source materials in the growth system, a high-quality 6H-SiC epilayer with an X-ray diffraction rocking curve (0006) full-width at the half maximum (FWHM) of 38 arcsec was obtained. We also carried out doping of nitrogen and boron during the growth of the SiC epilayer. A strong donor-acceptor pair (DAP) emission at a peak wavelength of 570 nm under excitation by a 395 nm nitride-based light-emitting diode (LED) was observed. The 6H-SiC with DAP emission is promising for use as a phosphor in a nitride-based LED, because high-quality nitride layers can be grown on the SiC substrates with small off-oriented angles.
Authors: Rui Jin Yu, Jin Young Park, Hyun Kyoung Yang, Byung Kee Moon, Byung Chun Choi, Jung Hyun Jeong
Abstract: A new deep red-emitting Mn2+-activated SrLaGa3S6O phosphor was first prepared by a solid-state reaction method. Their luminescence properties were investigated by photoluminescence excitation and emission spectra. The emission spectrum shows a broad band with an emission maximum at 668 nm under the host excitation of 340 nm. The full width at half maximum (FWHM) of the emission peak is about 83 nm. The CIE chromaticity coordinates (x = 0.673 and y = 0.312) shows that the phosphor emission is in the deep red region and were very near to the NTSC standard values for red. Since the excitation band of the phosphor lies in the near UV excitable region, giving a deep red emission, it can be used for applications in near UV phosphor converted white LED lighting and display devices.
Authors: Lin Yan Jia, Zhong Bao Shao, Yan Wen Tian
Abstract: The pure phase red phosphor yttrium borate doped with Eu3+ was prepared by a new solid state reaction named high temperature ball milling method. The phosphor was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence spectra. The results show that the single phase YBO3:Eu3+ phosphor was obtained at 600°C, which is obviously decreased in contrast to conventional solid state reaction method. The particles are approximately nanometer size with narrow distribution range and spherical morphology. In emission spectra, the strongest peak at 597nm is due to the transition 5D0→7F1 of Eu3+ ions under 394nm monitoring wavelength. The luminescent properties of YBO3:Eu3+ phosphor with 25 mol% doping concentration of Eu3+ is optimal.
Authors: Ye Qing Chen, Joo Hyun Lee, Sung Wook Park, Byung Kee Moon, Byung Chun Choi, Jung Hyun Jeong, Ki Wan Jang, Ho Sueb Lee, Soung Soo Yi
Abstract: In this paper, we report a successful synthesis of CaWO4:Eu3+ phosphor via an ethanol assisted hydrothermal process. X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FE-SEM) were used to investigate the growth of the products. The water and ethanol volume ratio is found to have extraordinary effect on the particle size and morphological appearance. Flower like ~ 1µm superstructures can be obtained with mixed solution of w/e of 50/50 at 120 °C hydrothermal sysnthesis for 12 h. High concentration of ethanol in aqueous solution was discovered to have a tendency in limiting the interaction between the small particles for crystallization. Temperature and time experiments were also performed to further investigate the growth mechanism of the ethanol assisted hydrothermal process. The photoluminescence properties of flower like CaWO4:Eu3+ has also been investigated.
Authors: Sheng Liu, Bei Ying Zhou, Shi Jia Gu, Lian Jun Wang, Wan Jiang, Wei Luo
Abstract: Two kinds of commercial LED phosphors (green phosphor LuAG:Ce3+ and red phosphor CaAlSiN3:Eu2+) with polymethyl methacrylate (PMMA) powders were mixed to prepare film phosphors with tunable emission peak in photoluminescence spectrum by flat vulcanizing machine under the temperature of 170 oC and pressure of 2 MPa. The physical phase, surface morphology, transmittance, luminescence spectra of samples were characterized by means of X-ray diffraction (XRD), Environmental scanning electron microscopy (ESEM), Ultraviolet-Visible (UV-Vis) spectrophotometry and Fluorescence spectrometer. The results show that the film phosphors phase was consistent with raw phosphors, phosphor particles were uniformly distributed, and fluorescence spectra with different proportions of phosphors in different position can be adjusted. Tested by HSP 3000 spectrum analyzer, the white LEDs fabricated by blue chip and composite film phosphor containing 5 wt% green phosphor and 1.5 wt.% red phosphor, which refers to the remote excitation technique, possessed color coordinate of (0.3715, 0.3280) and color rendering index (CRI) of 87 when it was driven at power of 36 V/140 mA, reaching the international advanced level.
Authors: Jae Moon Lee, Jeong Gon Yoo, Ji Sik Kim, Kee Sun Sohn
Abstract: An evolutionary optimization process involving a genetic algorithm and combinatorial chemistry (combi-chem) was tailored exclusively for the development of LED phosphors. The genetic algorithm assisted combi-chem (GACC) is a well-known, very efficient heuristic optimization method. Therefore the combination of a genetic algorithm and combi-chem would enhance the searching efficiency when applied to phosphor screening. The ultimate goal of our study was to develop oxide red and green phosphors, which are suitable for three-band white light emitting diodes (LED). In this regard, promising red and green phosphors for three-band white LED applications, such as Eu0.14Mg0.18Ca0.07Ba0.12B0.17Si0.32Od and Tb0.01Gd0.02Ce0.04B0.1Si0.83Od, were obtained.
Authors: Rong Feng Guan, Qin Qin Li, Shuai Mou Li
Abstract: The YAG yellow phosphor was synthesized by Co-precipitation Method and its luminescent properties were characterized. The Orthogonal Experiment results that under laboratory conditions, the prepared phosphor luminous intensity reached at the maximum and the optical properties of compound as white up to the best with blue-chip, when calcinations temperature up to 1600°C, sintering time is 3h, the Ce3+content is 0.05.Therefore, the phosphor could provide a theoretical basis for the design and development of white LED with luminescent materials, promoting the practical of white LED.
Authors: Yu Jie Chen, Feng Lan Han, Zhao Luo
Abstract: Na2BaMgP2O8 phosphors were synthesized by a standard solid state reaction and their luminescent properties were investigated. The phase structure was analyzed by X-ray powder diffraction measurement. Under the excitation of 365nm, Na2BaMgP2O8:Tb3+, Eu3+ phosphors show two color bands of green and red color due to 5D47F5 transition of Tb3+ ions and 5D07F2 transition of Eu3+ ions, respectively. The emission intensity of Tb3+ deceased with the increasing concentration of Eu3+, which verified that an effective energy transfer occurred from Tb3+ to Eu3+ in Na2BaMgP2O8 host. The present study indicated that the phosphors have a high potential application in solid state lighting.
Authors: Yan Dong, Yang Zhou, Xue Lin Han, Wei Jie Gu
Abstract: Mg doped BaAl12O19:Mn2+ phosphor is one of the most efficient green phosphors for PDP. It is difficult to prepare the phosphor both have small particle size (< 3μm) and high luminescence. In the present work, a BaAl12O19:Mn2+ phosphor with small particle size was synthesized by the chemical co-precipitation method. Phase transformation and particle growth process during calcining process were investigated. The nucleation process was also discussed. The results show that, the phase transformation is complicated, the transition phases include BaCO3, γ-Al2O3, BaF2, BaAl2O4 and two phases contain Mn; The BaAl12O19 phase is formed from the reaction between BaAl2O4 phase and γ-Al2O3 phase, no a-Al2O3 phase appears during the entire process; The formation temperature of pure BaAl12O19 phase is 1200°C, which is lower than that in the high-temperature solid state reaction method. High efficiency BaAl12O19:Mn2+ phosphor with small particle size (< 2μm) and hexagonal flaky shape can be prepared by this method.
Authors: Kyota Uheda
Abstract: Multiternary nitride and oxynitride compounds doped with rare earth ions, such as Eu2+ and Ce3+ have been enthusiastically applied as various phosphors to white LED. New red and green phosphors, CaAlSiN3:Eu and Ba3Si6O12N2:Eu, have been successfully synthesized, recently. The red phosphor has intense emission around 650 nm under two different irradiations at 405 and 455 nm from blue- and near UV-LED chips, respectively; while strong emission is observed around 520 nm from the green phosphor. Both phosphors also show small thermal quenching over the temperatures up to 150 °C. In addition, both LaSi3N5:Ce and La3Si8O4N11:Ce in lanthanum silicon nitride and oxynitride were examined as candidates for a blue phosphor in white LED with near UV-LED chip.
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