Byung Kee Moon

Korea Institute of Energy Research, Sŏul, Seoul, South Korea

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Publications (144)199.93 Total impact

  • Ceramics International 05/2014; 40(4):5693-5698. · 1.79 Impact Factor
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    ABSTRACT: A series of new double perovskite tungstate Ba2CaWO6:xDy(3+) (0.01⩽x⩽0.15) phosphors were synthesized via solid state reaction process. XRD analysis confirmed the phase formation of Ba2CaWO6:Dy(3+) materials. The photoluminescence excitation and emission spectra, concentration effect, thermal-quenching, and decay property were investigated. The phosphor could be excited by the UV light region from 250 to 400nm, and it exhibits blue (493nm) and yellow (584nm) emission corresponding to (4)F9/2-(6)H15/2 transitions and (4)F9/2-(6)H13/2 transitions, respectively. The optimum dopant concentration of Dy(3+) ions in Ba2CaWO6:xDy(3+) is around 5mol% and the critical transfer distance of Dy(3+) is calculated as 14Å. The thermal-quenching temperature is 436K for Ba2CaWO6:0.05Dy(3+). The fluorescence lifetime is also determined in Ba2CaWO6:0.05Dy(3+).
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 02/2014; · 1.98 Impact Factor
  • Journal of Luminescence 01/2014; · 2.14 Impact Factor
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    ABSTRACT: Y6(WMo)0.5O12 activated with Eu(3+) ions was investigated as a red-emitting conversion phosphor for white light emitting diodes (WLEDs). The phosphors were synthesized by calcining a citrate-complexation precursor at different temperatures. The photoluminescence properties of the phosphors and the energy transfer mechanisms involved were studied as a function of structure evolution. It was found that the host lattices were crystallized in a cubic or a hexagonal phase depending on the synthesis conditions. Although all the phosphors showed intensive red emission under an excitation of near-UV or blue light due to energy transfer from the host lattices to Eu(3+) ions, the photoluminescence spectra and temporal decay features were found to vary significantly with the structure and crystallinity of the host lattice. The mechanisms of the energy transfer from the host lattices to Eu(3+) ions and energy quenching among Eu(3+) ions were discussed on the basis of structure evolution of the host lattice. Phosphors calcined at 800 and 1300 °C were suggested to be promising candidates for blue and near-UV light excited WLEDs, respectively.
    Inorganic Chemistry 09/2013; · 4.59 Impact Factor
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    ABSTRACT: The phosphor of CeO2 activated with the trivalent rare-earth Sm3+ ions were synthesized by using a solvothermal method. The CeO2:Sm3+ powders were finally obtained through calcination process sintered in the air at 800-1200 degrees C. The synthesized phosphors were characterized systematically by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence (PL) and photoluminescence excitation spectra (PLE). The XRD and FE-SEM results reveal that the phosphor exhibit agglomerated spherical shape and with the increase of sintering temperature peaks become sharper and narrower and the crystal sizes also increase, respectively. The room temperature photoluminescence spectra of Sm3+ doped CeO2 powders were recorded on a PTI (Photon Technology International) flurimeter using a Xe-arc lamp with a power of 60 W. The emitted radiation was dominated by the orange light with the characteristic emission of Sm3+ from the transitions of 4G5/2 --> 6H5/2,7/2. The sharp emission properties show that the CeO2 has the potential to serve as a host material for rare-earth doped laser crystal and phosphor material.
    Journal of Nanoscience and Nanotechnology 09/2013; 13(9):6060-3. · 1.15 Impact Factor
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    ABSTRACT: By controlling the volume of HF and the alkaline earth ion introducing, a series of GdF3 samples have been synthesized by a hydrothermal method without any surfactant. The samples are characterized by X-ray diffraction (XRD) patterns, field emission scanning electron microscopy (FE-SEM) images, energy-dispersive spectroscopy (EDS) spectra, photoluminescence (PL) excitation and emission spectra as well as the luminescence dynamic decay curves. The optical properties of Tb3+ and the energy transfer from host Gd3+ to Tb3+ have been investigated and discussed in detail based on the volume of HF used in the synthesis procedure and the alkaline earth ion introducing. The experimental results suggest that the optical properties of Tb3+ can be controlled by the deliberately ion introducing as well as the volume of HF used in the synthesis procedure. Though the optical properties of Tb3+ can be adjusted by different ways, a green, easy, and cost saving way, such as deliberately ion introducing, is a good choice in modifying the optical properties of Tb3+.
    Optics Communications 08/2013; s 301–302:106–111. · 1.44 Impact Factor
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    ABSTRACT: Different concentrations of Tb3+ ion-doped gadolinium aluminum garnet (GAG) nanophosphors have been synthesized by solvothermal reaction method and sintered at 1300 °C. The XRD patterns confirm that the GAG phosphors sintered at 1300 °C have a garnet structure with single cubic phase. The calculated crystallite size is about 92 nm. The SEM images of the phosphors show the spherical morphology agglomerated with many small particles. The luminescence properties of these phosphors have been carried out by the emission and excitation spectra along with lifetime measurements. The excitation spectra of GAG:Tb3+ phosphors consist of three broad bands due to the 4f8→4f75d1 transition and some sharp peaks due to the 4f8→4f8 transition. The emission spectra of the phosphors reveal two colors, such as blue due to 5D3→7FJ transitions and green due to the 5D4→7FJ transitions. The dynamics of the phosphors have been investigated by decay curves and the cross-relaxation process and is observed at 0.5 mol% Tb3+ concentration.
    Journal of Luminescence 06/2013; · 2.14 Impact Factor
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    ABSTRACT: Eu3+ activated oxyapatite Ca2Gd8Si6O26 (CGS) nanophosphors were synthesized using a solvothermal reaction method. The structural and luminescent properties of these nanophosphors were investigated as a function of sintering temperature and Eu3+ ion concentration. The SEM images of the prepared phosphors reveal spherically shaped particles in the nanometer range and the XRD patterns confirm their hexagonal structure. The photoluminescence excitation (PLE) spectra of Eu3+:CGS showed the charge transfer band (CTB) and intense f–f transitions of Eu3+ and Gd3+. The intensity of the f–f transitions of Gd3+ increases with increasing the sintering temperature and decreases with increasing the Eu3+ concentration. It was observed that the CTB of Eu3+ shifted to a shorter wavelength region with an increase the crystallite size due to the variation of coordination environments. The photoluminescence (PL) spectra of Eu3+:CGS exhibit two emission lines corresponding to the 5D0 → 7F0 transition which results from occupation of Eu3+ ions in two different low symmetry local sites in CGS host lattice. The optimized sintering temperature and concentration of Eu3+ were observed for Eu3+:CGS nanophosphors based on the dominant red (5D0 → 7F2) emission intensity under NUV (395 nm) excitation. The decay curves of 5D0 level show that the lifetime decreases with increasing the crystallite size. These luminescent powders are expected to find potential applications such as WLEDs and optical display systems.
    Sensors and Actuators B Chemical 06/2013; · 3.54 Impact Factor
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    ABSTRACT: Bi3+ and Tb3+ ions co-doped GdAlO3 (GAP) nanophosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GAP phosphor confirms their orthorhombic phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of GAP:Tb3+, Bi3+ phosphors consist of a broad band in the shorter wavelength region due to the 4f8 → 4f75d1 transition of Tb3+ ions overlapped with the 6s2 → 6s16p1 (1S0 → 3P1) transition of Bi3+ ions and some sharp peaks in the longer wavelength region due to f → f transitions of Tb3+ ions. The present phosphors exhibit green color due to strong 5D4 → 7F5 transition of Tb3+ ions. The emission intensity was enhanced by co-doping with Bi3+ ions under 292 nm excitation, which indicate that the efficient energy transfer occurred from Bi3+ to Tb3+ ions.
    Materials Research Bulletin 06/2013; · 1.91 Impact Factor
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    ABSTRACT: The upconversion luminescence properties of ZrO2:Ho3+ and co-doped ZrO2:Ho3+, Yb3+ nanophosphors with various concentrations of Yb3+ ions were synthesized via a solvothermal reaction method. Our samples have a nearby spherical shape and an average crystal size was about 80 nm. For low concentrations of Yb3+ ion, the crystalline structure changed from tetragonal to monoclinic phase as the Yb3+ concentration increased to 3 mol% Yb3+ ions. As the Yb3+ concentration increased to above 5 mol%, ZrO2 nanophosphors displayed a very stable tetragonal phase. The sample shows a strong green (550 nm) and weak red (660 nm) and near infrared (757 nm) upconversion emission corresponding to the transitions of Ho3+:5F4/5S2 --> 5I8, 5F5 --> 5I8 and 5S2 --> 5I7, respectively. The energy transfer (ET) processes between the Ho3+ and Yb3+ ions and the involved mechanisms have been investigated. Experimental results suggest that two-photon upconversion processes are taking place under excitation by a 975 nm.
    Journal of Nanoscience and Nanotechnology 06/2013; 13(6):4006-9. · 1.15 Impact Factor
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    ABSTRACT: A series of Zn1−xGa2S4:xMn2+ (0.005 ≤ x ≤ 0.08) phosphors has been synthesized by solid-state reaction at 950 °C for 2 h in a flowing H2S stream. The structural and photoluminescence properties of Zn1−xGa2S4:xMn2+ phosphors have been investigated. Under an excitation wavelength of λex = 336 nm, ZnGa2S4:Mn2+ exhibits a red emission band at about 612 nm owing to the Mn2+4T1(4G) → 6A1(6S) transition. The luminescence band shifts to longer wavelength and is accompanied by a decrease in decay time with increasing Mn2+ concentration. The maximum PL intensity of the phosphor is obtained at x = 0.03. The critical transfer distance of Mn2+ is calculated as 21 Å. The decay time for ZnGa2S4:0.03Mn2+ is 1.79 ms. The calculated CIE coordinates indicate that ZnGa2S4:Mn2+ has good color purity. Mn2+-activated ZnGa2S4 phosphors have great potential for application in UV white LED and display devices.
    Materials Research Bulletin. 06/2013; 48(6):2154–2158.
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    ABSTRACT: A new thiogallate-based green-emitting phosphor, MgGa2S4:Eu2+, was first synthesized via a high-temperature solid-state reaction in a CS2 atmosphere. We then investigated the structures and luminescent properties of the MgGa2S4:Eu2+ phosphors. The MgGa2S4:Eu2+ phosphors can be excited efficiently by UV–visible light in the wavelength range from 350 to 520 nm and they emit an intensely green light with emission bands peaking at 538 nm. The optimal concentration for Eu2+ in MgGa2S4 was found to be about 6 mol%, and the corresponding concentration quenching mechanism was the electric multipole–multipole interaction. The quenching temperature was calculated to be 402 K, and the Huang–Rhys factor was about 4. The energy barrier for thermal quenching was calculated to be 0.28 and 0.27 eV by the two types of the Arrhenius equations. The small variation in the color coordinates of MgGa2S4:Eu2+ under high temperatures indicates that the as-synthesized phosphor has good color stability. Due to their broadband absorption in the 350–520 nm wavelength range, these phosphors may be able to fulfill the requirements for application in the development of Ga(In)N-based white LEDs.
    Journal of the American Ceramic Society 06/2013; 96(6). · 2.11 Impact Factor
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    ABSTRACT: Through a polyethylene glycol (PEG) assisted hydrothermal method, the REF3–KF system materials have been synthesized. The crystalline structure and the morphology of the final products can be divided into three groups. With the molar ratio of REF3 to KF = 1:0, 1:1, and 3:1 in the final products, the samples crystallize in the hexagonal phase (REF3, RE = La, Ce, Pr, and Nd), the cubic phase (KREF4, RE = Sm, Eu, Gd, Tb, and Dy), and the tetragonal phase (KRE3F10, RE = Ho, Er, Tm, Yb, and Y), respectively. The enhanced luminescence of Tb3+ has been observed in the Ce3+/Tb3+ co-doped samples and the CeF3 sample. Acting as a probe, the Eu3+ presents different optical properties in the tetragonal phase of KY3F10 and in the cubic phase of KEuF4. In addition, the luminescent concentration effects of Tb3+ and Eu3+ have also been observed in KTbF4 and KEuF4 samples and the luminescent decay curves prove those.
    Materials Chemistry and Physics. 05/2013; 139(s 2–3):609–615.
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    ABSTRACT: Rare earth molybdates R4MoO9 (R = Y, Gd, and Lu) with Eu3+ ion-doped were synthesized by solid-state reaction. The phase structure, optical absorption and photoluminescence properties of the as-prepared powder samples were studied. The powder X-ray diffraction patterns indicated that all the compounds crystallized in a hexagonal structure, and the lattice parameters reduced in the order of the ionic radii of R. The UV–visible diffuse reflectance spectra revealed that the compounds had a strong absorption of near-UV light due to the excitation of MoO6 groups in the host lattices. The energy absorbed by the host lattices could then be transferred to doped Eu3+ ions, resulting in red emission due to the f–f transitions of Eu3+ ions. The optical absorption and photoluminescence properties of the compounds indicated that they might be candidates as the color-conversion red phosphors for solid-state lighting.
    Materials Chemistry and Physics. 05/2013; 139(s 2–3):998–1002.
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    ABSTRACT: By using a hydrothermal method, a series of Eu3+ concentration dependent GdF3 nanocrystals have been synthesized. The crystalline structures of samples are characterized by XRD patterns, the morphology and size of the samples are illustrated by FE-SEM images, and the optical properties of the samples are presented by PL excitation and emission spectra. The energy transfer from host Gd3+ to Eu3+ is observed in the Eu3+ doped GdF3 nanocrystals. The optical properties of Eu3+ and the energy transfer efficiency from host Gd3+ to Eu3+ are discussed on the basis of the Eu3+ concentration dependent integrated PL excitation and emission spectra of Gd3+ and Eu3+. The discussion on optical properties of Eu3+ and the energy transfer from Gd3+ to Eu3+ is meaningful to design and synthesize Gd3+ based compounds.
    Solid State Sciences. 05/2013; 19:99–103.
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    ABSTRACT: ZnO nanoparticles (NPs) with rod, bullet and broom-like morphologies have been synthesized by the solvothermal method. Structural analysis revealed ZnO NPs to be of the single crystal wrutzite hexagonal structure. Their size and morphology were controlled by varying the polarity of solvents. The aspect ratio of ZnO NPs at the lower polarity was below 2, and their shape was like a bullet. When increasing the polarity of solvent, the aspect ratio also increases and the shape changes to a rod-like morphology. This process is very simple and scalable. In addition, it can be used for fundamental studies of the tunable morphology formation.
    Ceramics International 01/2013; 39:6599-6606. · 1.79 Impact Factor
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    ABSTRACT: ZrO2:Er3+ and ZrO2:Er3+,Yb3+ phosphors were synthesized via a solvothermal reaction method. For low concentrations of Yb3+, the crystalline structure changed from the tetragonal to monoclinic phase as sintering temperature increased. As the Yb3+ concentration increased to a value above 0.05 mol, ZrO2 phosphors displayed a very stable tetragonal phase. The green and red upconversion emissions of ZrO2:Er3+,Yb3+ phosphors were measured under the excitation with a 975 nm continuous wave diode laser, and the pump power dependence of upconversion intensity was investigated. As the Yb3+ concentration increased from 0 to 0.05 mol, the red upconversion emission intensity increased more rapidly than the green emission intensity. This is attributed to the energy transfer (4I11/2→4I15/2:4I_{13/2}→4F9/2) between Er3+ ions and the energy back transfer [4S3/2:4I_{13/2(Er3+)}→2F7/2:2F_{5/2(Yb3+)}] between the Er3+ and Yb3+ ions. In this case, the pump power dependence of red emission intensity changed from quadratic to linear as Yb3+ concentration increased.
    Japanese Journal of Applied Physics 01/2013; 52(1). · 1.07 Impact Factor
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    ABSTRACT: The color rendering index (CRI) and structural stability of cerium doped yttrium aluminum garnet (YAG:Ce) based phosphors have been enhanced by replacing Y3+ ions by larger radius ions (Tb3+, Gd3+, Eu3+, and Sm3+) at the dodecahedral site and replacing Al3+ ions by larger ones (Ga3+, Y3+, Tb3+, Gd3+, and Sm3+) at the octahedral site. These aluminum garnet crystalline powders were prepared by solvothermal reaction method at 300 °C for 48 h. The lattice constant values of synthetic aluminum garnet crystalline powders are larger than that of YAG and the emission wavelength of Ce3+ ion of these samples is longer than that of YAG:Ce. FESEM and TEM studies revealed that the Ln3Ga2Al3O12 and Ln3Al2Al3O12 crystalline powders have 3-dimensional star-like morphology with submicron size and good crystallinity, while, Ln3(LnAl)Al3O12 garnet crystalline powders were cubic crystalline phases and shaped as cubes with the round edge having an approximate diameter of about 200–400 nm. All the prepared powders were grown along (100) direction and crystallized into single crystal. Also, the effects of treatment time and reaction temperature on the structure of aluminum garnet crystalline powders have been investigated.
    Current Applied Physics 01/2013; 13(3):441-447. · 1.81 Impact Factor
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    ABSTRACT: Through a polyethylene-glycol-assisted hydrothermal method, a series of potassium fluoride (KF)–Yttrium (III) fluoride (YF3) system materials have been synthesized. By controlling the reactant ratios of KF: rare earth ions (RE3+), the hydrothermal temperatures, and the pH values of the prepared solutions, the final products can evolve among the orthorhombic phase of YF3 and/or the tetragonal phase of potassium triyttrium decafluoride (KY3F10) and/or the cubic phase of potassium yttrium tetrafluoride (KYF4). The final products are characterized by the x-ray diffraction (XRD) patterns, the field-emission scanning electron microscopy (FE-SEM) images, the energy-dispersive spectroscopy (EDS) patterns, the photoluminescence (PL) spectra, and the luminescent dynamic decay curves. The XRD patterns of the samples suggest the phase evolution of the final products. The FE-SEM images and the EDS patterns prove that. Europium ion (Eu3+) acting as a probe, its PL spectra and the luminescent decay curves all put together prove the phase evolution of the final products. The research can be extended to study the other KF–REF3 system materials.
    Journal of Materials Research 12/2012; 27(23):2988-2995. · 1.71 Impact Factor
  • physica status solidi (a) 12/2012; 209(12):2620-2625. · 1.21 Impact Factor

Publication Stats

85 Citations
51 Downloads
199.93 Total Impact Points

Institutions

  • 2013
    • Korea Institute of Energy Research
      Sŏul, Seoul, South Korea
    • Liaocheng Teachers University
      Tungchangfu, Shandong Sheng, China
    • Dong-Eui University
      • Department of Physics
      Pusan, Busan, South Korea
  • 1999–2013
    • Pukyong National University
      • Department of Physics
      Pusan, Busan, South Korea
  • 2011
    • Jinggangshan University
      Jiang’an, Jiangsu Sheng, China
  • 2005
    • Silla University
      Tsau-liang-hai, Busan, South Korea