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Synthesis and Characterization of the Intense Red Phosphor AgEu(MoO4)2 for Blue GaN-Based LED Chips
Chongfeng Guo,Tao Chen,Lin Luan,양현경,최병춘,정중현 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2
The intense red-emitting phosphor AgEu(MoO4)2 was prepared by using a sol-gel method. The crystallization process of the precursors was characterized by using a thermogravimetry-differential thermal analysis (TG-DTA) and X-ray diffraction (XRD). The size distribution and the shape of the phosphors were characterized by using a field emission scanning electron microscopy (FE- SEM). The samples obtained by using the sol-gel method had a smaller size, a more regular shape and a narrower particle size distribution than those obtained by using the solid-state method. The photoluminescent excitation spectrum of the AgEu(MoO4)2 phosphor is different from there of other double molybdates AEu(MoO4)2 (A = alkali metal ions) phosphors and its strongest absorption is located at 465-nm. The phosphor AgEu(MoO4)2 shows a strong red emission at 616 nm under excitation of 465 nm blue light, which matches well with commercial blue-light-emitting diodes (LEDs); thus, it is an excellent red phosphor candidate for white LEDs with blue light chips.
Preparation and luminescence of blue-emitting phosphor Ca2PO4Cl:Eu2+ for n-UV white LEDs
Ruijin Yu,Chongfeng Guo,Ting Li,Yan Xu 한국물리학회 2013 Current Applied Physics Vol.13 No.5
A series of blue-emitting Ca2 xEuxPO4Cl phosphors were synthesized by a solid state method in a reducing atmosphere. The factors those affect the structure and the photoluminescence (PL) intensities of phosphors,including the dosage of chlorine source CaCl2, reaction time and annealing temperature, have been investigated in detail. X-ray diffraction (XRD) and photoluminescence measurements were performed to testify the crystal structure and luminescent properties. The optimal Eu2þ concentration was determined, and the mechanism of the concentration quenching was predominated by dipoleedipole interaction. The present phosphor exhibits a strong absorption in the near-UV region, emits an intense blue emission centered at 451 nm and presents excellent thermal stability, suggesting that the phosphor is competitive as a promising blue-emitting phosphor for near ultraviolet (n-UV) light-emitting diodes (LEDs).
Jing, Heng,Guo, Chongfeng,Zhang, Gongguo,Su, Xiangying,Yang, Zheng,Jeong, Jung Hyun The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.27
<P>Ce<SUP>3+</SUP>-doped Ba<SUB>2</SUB>Ln(BO<SUB>3</SUB>)<SUB>2</SUB>Cl (Ln = Gd, Y) phosphors were synthesized through a conventional high-temperature solid state method in CO atmosphere. Structural and spectroscopic characterizations of the samples have been performed by X-ray diffraction and photoluminescence spectra measurements. The phosphors can be efficiently excited by near ultraviolet (n-UV) light resulting in blue emission. The optimal Ce<SUP>3+</SUP> dopant concentrations in both compounds were determined, and the concentration quenching mechanisms were also discussed. The photoluminescence excitation (PLE) and emission (PL) spectra, and decay curves at liquid helium temperature were measured to analyze the crystallographic occupancy sites of Ce<SUP>3+</SUP> in the Ba<SUB>2</SUB>Ln(BO<SUB>3</SUB>)<SUB>2</SUB>Cl (Ln = Gd, Y) hosts. The thermal stabilities of the phosphors Ba<SUB>2</SUB>Ln(BO<SUB>3</SUB>)<SUB>2</SUB>Cl:Ce<SUP>3+</SUP> (Ln = Gd, Y) were studied using the dependence of the luminescence intensities on temperature (300–500 K), and their luminescence quenching temperatures and thermal activation energies were also determined. The results indicate that the phosphor Ba<SUB>2</SUB>Gd(BO<SUB>3</SUB>)<SUB>2</SUB>Cl:Ce<SUP>3+</SUP> offers excellent optical properties as a potential blue-emitting phosphor candidate for n-UV LEDs, such as a higher thermal stability and a stronger luminescence intensity, than those of the phosphor Ba<SUB>2</SUB>Y(BO<SUB>3</SUB>)<SUB>2</SUB>Cl:Ce<SUP>3+</SUP>.</P> <P>Graphic Abstract</P><P>Ce<SUP>3+</SUP>-doped Ba<SUB>2</SUB>Ln(BO<SUB>3</SUB>)<SUB>2</SUB>Cl (Ln = Gd, Y) phosphors were synthesized through a conventional high-temperature solid state method in CO atmosphere. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm32761a'> </P>
Enhanced luminescence of Tb3+ by efficient energy transfer from Ce3+ in Sr2B5O9Cl host
Jiming Zheng,Chongfeng Guo,Xu Ding,Zhaoyu Ren,Jintao Bai 한국물리학회 2012 Current Applied Physics Vol.12 No.3
Ce3+ and Tb3+ co-doped Sr2B5O9Cl phosphors with intense green emission were prepared by the conventional high-temperature solid-state reaction technique. A broad band centered at about 315 nm was found in phosphor Sr2B5O9Cl: Ce3+, Tb3+ excitation spectrum, which was attributed to the 4f-5d transition of Ce3+. The typical sharp line emissions ranging from 450 to 650 nm were originated from the 5D4/7FJ (J ¼ 6, 5, 4, 3) transitions of Tb3+ ions. The photoluminescence (PL) intensity of green emission from Tb3+ was enhanced remarkably by co-doping Ce3+ in the Tb3+ solely doped Sr2B5O9Cl phosphor because of the dipoleedipole mechanism resonant energy transfer from Ce3+ to Tb3+ ions. The energy transfer process was investigated in detail. In light of the energy transfer principles, the optimal composition of phosphor with the maximum green light output was established to be Sr1.64Ce0.08Tb0.1Li0.18B5O9Cl by the appropriate adjustment of dopant concentrations. The PL intensity of Tb3+ in the phosphor was enhanced about 40 times than that of the Tb3+ single doped phosphor under the excitation of their optimal excitation wavelengths.
The Vis-NIR multicolor emitting phosphor Ba4Gd3Na3(PO4)6F2: Eu2+, Pr3+ for LED towards plant growth
Ziwei Zhou,Niumiao Zhang,Jiayu Chen,Xianju Zhou,Maxim S. Molokeev,Chongfeng Guo 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.65 No.-
Photosynthesis process is the basic for plant growth, which needs energy from the light. The pigments of chlorophyll a, b and bacteriochlorophyll are responsible for the absorption of light, in which blue, red and near-infrared (NIR) light directly or indirectly promote the plant growth and enhancement of nurtiments. It is important for plant to support absorbable light, and phosphhor-converted light emitting diodes (pc-LEDs) are low-cost, energy-saving and enviromental friendly devices for plant growth. To develop a phosphor with emission covering the blue, red and NIR, a series of phosphors Ba4Gd3Na3(PO4)6F2: Eu2+, Pr3+ with blue, red and NIR multi-emitting were prepared. Their emissions not only match well with the absorption spectra of pigments in the plant, but also could be excited by near ultraviolet (n-UV) LED chip. The crystal structure of host Ba4Gd3Na3(PO4)6F2 was refined from the XRD data and three different crystallographic sites occupied by Eu2+ were determined through low temperature photoluminescence spectra. The energy transfer from Eu2+ to Pr3+ ions was also discussed in detail. Results indicated that the multi-emitting Ba4Gd3Na3(PO4)6F2: Eu2+, Pr3+ can serve as a phosphor candidate for plant growth LEDs.