The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Qinyuan Zhang - One of the best experts on this subject based on the ideXlab platform.
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luminescence properties and warm white Led Application of a ternary alkaline fluoride red phosphor k2naalf6 mn4
Dalton Transactions, 2017Co-Authors: L Y Wang, E H Song, Tingting Deng, Yingling Zhou, Z F Liao, Weiren Zhao, B Zhou, Qinyuan ZhangAbstract:Herein, a Mn4+ ion doped complex ternary-alkaline fluoride red phosphor K2NaAlF6:Mn4+ has been synthesized through a facile two-step co-precipitation method at room temperature. The crystal structure, morphological properties and influence of the dopant concentration, temperature and humidity on luminescence properties as well as the performance of the as-synthesized phosphor used in white light emitting diodes (WLeds) were investigated carefully. Intense absorption in the blue region (∼460 nm) and bright narrow-band red emission (∼630 nm) with high color purity were observed from this resultant powder. Temperature-dependent investigation and reliability examination in a HTHH environment (85 °C high temperature and 85% high humidity) indicate that the obtained ternary-alkaline fluoride phosphor K2NaAlF6:Mn4+ presents more exceptional thermal quenching behavior and longevity compared to some other binary-alkaline fluorides. Moreover, using K2NaAlF6:Mn4+ as a red light component, a warm WLed with a preferable color rendering index (Ra = 85.5) and luminous efficacy (LE = 91.2 lm W−1) as well as a low corresponding color temperature (CCT = 3650 K) is easily achieved, further revealing the great potential of the as-prepared ternary-alkaline fluoride red phosphor K2NaAlF6:Mn4+ for WLed Applications.
Menglian Gong - One of the best experts on this subject based on the ideXlab platform.
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properties structure relationship research on licapo4 eu2 as blue phosphor for nuv Led Application
Journal of Alloys and Compounds, 2013Co-Authors: Xinguo Zhang, Liya Zhou, Menglian GongAbstract:Abstract Blue-emitting phosphors of Eu2+-activated LiCaPO4 with a hexagonal structure were prepared via a conventional solid-state method. The XRD, PL spectra and thermal quenching were applied to characterize the phosphors. The crystallographic site of Eu2+ ion in the LiCaPO4 lattice was identified and discussed. The optimized LiCaPO4:0.03Eu2+ exhibits the bright greenish-blue emission with CIE coordinates of (0.119, 0.155) and a quantum efficiency of 52%. The critical energy-transfer distance was confirmed as ∼18 A by both calculated crystal structure method and experimental spectral method. The thermal stability of LiCaPO4:Eu2+ was evaluated by temperature-dependent PL spectra, and the thermal quenching mechanism was found to be thermal assisted ionization. Prototype blue Leds with high color purity and good current stability were fabricated.
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concentration quenching of eu2 in a thermal stable yellow phosphor ca2bo3cl eu2 for Led Application
Journal of Luminescence, 2012Co-Authors: Xinguo Zhang, Jilin Zhang, Zhiyue Dong, Jianxin Shi, Menglian GongAbstract:Abstract A piece-shaped phosphor Ca2BO3Cl: Eu2+ was synthesized by solid-state reaction method. This phosphor exhibited wide absorption in ultra-violet and visible range, and bright yellow emission band centering at 570 nm. The concentration quenching mechanism was verified to be a dipole–dipole interaction, and its critical transfer distance was about 17 A by both calculated crystal structural method and experimental spectral method. This phosphor has a good thermal stability with a quenching temperature (T1/2) of 200 °C. Yellow and white Leds were fabricated with this phosphor and near UV chips, and the yellow Led has a high color purity of 97.0% and promising current tolerant property, while the white Led shows a luminous efficiency of 11.68 lm/W.
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a new red emitting ce3 mn2 doped barium lithium silicate phosphor for nuv Led Application
Materials Letters, 2011Co-Authors: Xinguo Zhang, Menglian GongAbstract:Abstract A series of new red-emitting Ce 3+ , Mn 2+ -doped barium lithium silicate phosphors, with general formula Ba 2 Li 2 Si 2 O 7 : Ce 3+ , Mn 2+ , were synthesized by solid-state reactions. The Mn 2+ in this system can be effectively excited in a wide UV region especially in the NUV range, and has broad red emission after NUV excitation through Ce 3+ –Mn 2+ energy transfer, as well as excellent thermal stability. The blue-shift behavior of Mn 2+ emission with increasing temperature can be described in terms of the phonon–electron interaction. The promising luminescence properties make it a red candidate for Application in NUV chip pumped Led.
Ariyuki Kato - One of the best experts on this subject based on the ideXlab platform.
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Luminescence properties of Li2SrSiO4:Eu2+ silicate yellow phosphors with high thermal stability for high-power efficiency white Led Application
Journal of Luminescence, 2019Co-Authors: Siti Sarina Binti Nasir, Akihiro Tanaka, Shuto Yoshiara, Ariyuki KatoAbstract:Abstract Li2SrSiO4:Eu2+ yellow phosphors were synthesized by Polymerized Complex Method using TEOS and their thermal stability was investigated. The synthesized phosphors exhibited a broad yellow emission band around 560 nm. The optimum H2/N2 reduction temperature and Eu concentration are 900 °C and 0.5% respectively, which show the highest PL intensity and 6 times higher than samples synthesized by conventional solid-state reaction at the same condition. In order to investigate the thermal stability, PL properties in temperature range from 16.4 K to 583 K were examined. The PL intensity remains 80% above at high temperature (438 K) compared with room temperature. Activation energy and internal quantum efficiency of samples are estimated to be 0.43 eV and 62% respectively. Emission processes in Li2SrSiO4:Eu2+ phosphor were discussed with configuration coordinate model. The results reveal that Li2SrSiO4:Eu2+ yellow phosphors shows excellent thermal stability and have feasibility in replacement of YAG:Ce3+ yellow phosphors in white Leds Application.
Xinguo Zhang - One of the best experts on this subject based on the ideXlab platform.
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properties structure relationship research on licapo4 eu2 as blue phosphor for nuv Led Application
Journal of Alloys and Compounds, 2013Co-Authors: Xinguo Zhang, Liya Zhou, Menglian GongAbstract:Abstract Blue-emitting phosphors of Eu2+-activated LiCaPO4 with a hexagonal structure were prepared via a conventional solid-state method. The XRD, PL spectra and thermal quenching were applied to characterize the phosphors. The crystallographic site of Eu2+ ion in the LiCaPO4 lattice was identified and discussed. The optimized LiCaPO4:0.03Eu2+ exhibits the bright greenish-blue emission with CIE coordinates of (0.119, 0.155) and a quantum efficiency of 52%. The critical energy-transfer distance was confirmed as ∼18 A by both calculated crystal structure method and experimental spectral method. The thermal stability of LiCaPO4:Eu2+ was evaluated by temperature-dependent PL spectra, and the thermal quenching mechanism was found to be thermal assisted ionization. Prototype blue Leds with high color purity and good current stability were fabricated.
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concentration quenching of eu2 in a thermal stable yellow phosphor ca2bo3cl eu2 for Led Application
Journal of Luminescence, 2012Co-Authors: Xinguo Zhang, Jilin Zhang, Zhiyue Dong, Jianxin Shi, Menglian GongAbstract:Abstract A piece-shaped phosphor Ca2BO3Cl: Eu2+ was synthesized by solid-state reaction method. This phosphor exhibited wide absorption in ultra-violet and visible range, and bright yellow emission band centering at 570 nm. The concentration quenching mechanism was verified to be a dipole–dipole interaction, and its critical transfer distance was about 17 A by both calculated crystal structural method and experimental spectral method. This phosphor has a good thermal stability with a quenching temperature (T1/2) of 200 °C. Yellow and white Leds were fabricated with this phosphor and near UV chips, and the yellow Led has a high color purity of 97.0% and promising current tolerant property, while the white Led shows a luminous efficiency of 11.68 lm/W.
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a new red emitting ce3 mn2 doped barium lithium silicate phosphor for nuv Led Application
Materials Letters, 2011Co-Authors: Xinguo Zhang, Menglian GongAbstract:Abstract A series of new red-emitting Ce 3+ , Mn 2+ -doped barium lithium silicate phosphors, with general formula Ba 2 Li 2 Si 2 O 7 : Ce 3+ , Mn 2+ , were synthesized by solid-state reactions. The Mn 2+ in this system can be effectively excited in a wide UV region especially in the NUV range, and has broad red emission after NUV excitation through Ce 3+ –Mn 2+ energy transfer, as well as excellent thermal stability. The blue-shift behavior of Mn 2+ emission with increasing temperature can be described in terms of the phonon–electron interaction. The promising luminescence properties make it a red candidate for Application in NUV chip pumped Led.
Jae Soo Yoo - One of the best experts on this subject based on the ideXlab platform.
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Optical characteristics and longevity of the line-emitting K_2SiF_6:Mn^4+ phosphor for Led Application
Optical Materials Express, 2016Co-Authors: Ji Wook Moon, Bong Gul Min, Jin Sung Kim, Myoung Su Jang, Kwan-young Han, Jae Soo YooAbstract:Optical properties of the line-emitting K2SiF6:Mn4+ phosphor were investigated for Led Application. The color coordinate on the CIE chromaticity diagram, photoluminescence (PL), excitation characteristics and decay time of the K2SiF6:Mn4+ phosphor were measured and compared with those of the CaAlSiN3:Eu2+ red phosphor. Then, a set of white Leds were fabricated based on these two red phosphors. The K2SiF6:Mn4+-loaded white Led is found to have big advantages over the CaAlSiN3:Eu2+-loaded white Led in the luminous flux and the color gamut. Its longevity and the color variation are inferior to its counterpart at 85°C, 85% relative humidity test. However, it is demonstrated in this work that they are improved much by blending two phosphors for white Led Application while keeping its performance. Also, it is discussed on how longevity of the K2SiF6:Mn4+ phosphor is improved.
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Tuning the Optical Properties of ( Sr , Ba ) 3Si6O3N8 : Eu Phosphor for Led Application
Journal of The Electrochemical Society, 2011Co-Authors: Hyunju Lee, Kyung Pil Kim, D Suh, Jae Soo YooAbstract:Highly efficient green-emitting (Sr,Ba) 3 Si 6 O 3 N 8 :Eu phosphors are prepared by solid-state reaction. Their optical properties are adjusted to be suitable for white light-emitting diode (Led) Application. It is found that there are two ways to efficiently tune the excitation and emission spectra of this material system. One method is to adjust the ratio of Sr 2+ ions to Ba 2+ ions in the host lattice. The other method is to control the europium concentration. The luminescent intensity of the phosphor sample is optimized at Sr 2.8 Ba 0.2 Si 6 O 3 N 8 :Eu 0.2 . In this case, a synergy effect in the photoluminescence intensity is observed when substituting Ba 2+ for Sr 2+ ions while keeping the Sr 3 Si 6 O 3 N 8 crystal structure as the dominant phase. The excitation spectrum of the phosphor sample is broad due to the 4f-5d transitions, which is favorable to InGaN chip Application. Also, an emission wavelength is easily tuned to the peak wavelength of 538 nm with the full width of half-emission maximums of 77 nm. Temperature-dependent photoluminescence intensity exhibits a low thermal quenching. We believe that this green oxynitride phosphor can be used as a solid-state lighting source.
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Longevity Improvement of CaS:Eu Phosphor Using Polymer Binder Coating for White Led Application
Journal of The Electrochemical Society, 2008Co-Authors: I. W. Park, Jung Han Kim, Jae Soo Yoo, H. H. Shin, Chang-dong Kim, C. K. ChoiAbstract:To improve the longevity of a phosphor converted white light-emitting diode (Led), the SiO 2 coating on CaS:Eu phosphor by using polymer binder was carried out. The coating characteristics were found to be critically dependent on the sort of monomer and temperature of the reaction during the polymerizing process. This process is found to avoid a hydrolysis reaction, which causes damage to CaS:Eu phosphor surface, which frequently occurs in the conventional sol-gel process. Field-emission scanning electron microscope images and transmission electron microscopy images showed that polymer binder coating of SiO 2 on CaS:Eu phosphor was very solid and could well serve as a protective layer against the moisture, which is critically detrimental to the development of commercial white Leds. Significant optical stability, even after a moisture-contacting experiment, was observed in the case of coated phosphors. However, it was also found that the emission of H 2 S from the CaS:Eu phosphor still remained influential to the longevity of an Led device because of a bottom Ag plate in our experimental regime.
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Spectral dependency of Eu2+-activated silicate phosphors on the composition for Led Application
Korean Journal of Chemical Engineering, 2006Co-Authors: Sang Hyeon Kim, Hyo Jin Lee, Kyeong Phil Kim, Jae Soo YooAbstract:An Sr2SiO4-Ba2SiO4 material system doped by Eu2+ was studied for light emitting diodes (Leds) Application. The main concern was the precise control of excitation and emission spectra for maximum light yield and color coordinate, which was carried out by changing the composition of the alkaline earth ions in host lattice. The Sr2SiO4 : Eu-Ba2SiO4 : Eu system was found to be excellent for white Led Applications with excitation in the 380–465 nm region. Especially, the yellow light intensity from (Sr,Ba)SiO4 : Eu phosphors was comparable to YAG : Ce phosphors in case of blue Led excitation.