Hong Chae Jung

Pukyong National University, Tsau-liang-hai, Busan, South Korea

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Publications (21)54.75 Total impact

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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 08/2013; 39:6599-6606. DOI:10.1016/j.ceramint.2013.01.095 · 2.09 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; DOI:10.1016/j.snb.2010.02.056 · 4.29 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; DOI:10.1016/j.materresbull.2010.01.016 · 2.29 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; DOI:10.1016/j.jlumin.2009.10.017 · 2.37 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 05/2013; 13(3-3):441-447. DOI:10.1016/j.cap.2012.09.001 · 2.03 Impact Factor
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    ABSTRACT: Nanocrystalline Ca2Gd8Si6O26 (CGS): Sm3+ phosphors were synthesized by solvothermal reaction method. The structural and morphological properties of the samples were evaluated by X‐ray diffraction and scanning electron microscopy. The photoluminescence excitation and emission spectra along with decay properties were investigated as a function of Sm3+ concentration. Under 405 nm excitation wavelength, the photoluminescence spectra showed three emission peaks at 565 nm (4G5/2 → 6H5/2) and at 650 nm (4G5/2 → 6H9/2), and with an intense orange emission at 600 nm (4G5/2 → 6H7/2). Based on the orange emission performance, the Sm3+ concentration was optimized to be at 2 mol%. The low voltage cathodoluminescence (CL) properties were also performed for 2 mol% Sm3+‐doped CGS phosphors as a function of accelerating voltage (1–5 kV). From the CL spectra, the reddish‐orange emission was observed. The calculated Commission International De I‐Eclairage chromaticity coordinates are in close proximity to the chromaticity coordinates of Nichia corporation developed amber light emitting diodes.
    Journal of the American Ceramic Society 01/2012; 95(1-1):238-242. DOI:10.1111/j.1551-2916.2011.04762.x · 2.43 Impact Factor
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    ABSTRACT: Blue and green light emissive nanocrystalline Ca2Gd8Si6O26 (CGS):Tm3+ and CGS:Er3+ phosphors with high color purity were prepared by solvothermal reaction method. The structural and morphological properties of these phosphors were evaluated by the powder X-ray diffraction (XRD) and scanning electron microscopy, respectively. From the XRD results, Tm3+:CGS and Er3+:CGS phosphors had the characteristic peaks of oxyapatite in the hexagonal lattice structure. The visible luminescence properties of phosphors were obtained by ultraviolet (UV) or near-UV light and low voltage electron beam (0.5–5kV) excitation. The photoluminescence and cathodoluminescence properties were investigated by changing the variation of Tm3+ or Er3+ concentrations and the acceleration voltage, respectively. The CGS:Tm3+ phosphors exhibited the blue emission due to 1D2→3F4 transition, while the CGS:Er3+ phosphors showed the green emission due to 4S3/2→4I15/2 transition. The color purity and chromaticity coordinates of the fabricated phosphors are comparable to or better than those of standard phosphors for lighting or imaging devices.
    Journal of Alloys and Compounds 07/2011; 509(27):7537-7542. DOI:10.1016/j.jallcom.2011.04.122 · 2.73 Impact Factor
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    ABSTRACT: The cathodoluminescence and the excitation induced photoluminescence properties have been investigated for the nanocrystalline Tb3+/Sm3+:Ca2Gd8Si6O26 phosphors prepared by a solvothermal reaction method. The XRD patterns confirm their hexagonal structure. The green, orange and white emissions have been obtained by exciting at 275, 378, and 405 nm wavelengths, respectively. The corresponding CIE chromaticity coordinates are found to be in close proximity to the standard points in their respective regions. The cathodoluminescence at low accelerating voltage has also covered the entire visible region, resulting in white emission. These luminescent powders are expected to find potential applications in the development of LEDs and FEDs.
    Journal of Materials Chemistry 05/2011; 21(17-17):6136-6139. DOI:10.1039/c0jm04337k · 7.44 Impact Factor
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    ABSTRACT: Different concentrations of trivalent praseodymium (Pr3+) ions activated GdAlO3 nanophosphors were synthesized by solvothermal reaction method. Thermogravimetric/differential thermal analysis (TG/DTA) and X-ray diffraction (XRD) measurements were used to investigate the phase transformations that occur during the preparation of these phosphors. The morphology of the powder after heat treatment was observed by scanning electron microscopy (SEM). The luminescent studies on these compounds have been carried out from the measurements of their photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The PL spectra show blue-green emission corresponding to the f–f transitions of Pr3+ (3P0 → 3H4) and red emission corresponding to the f–f transition of Pr3+ (3P0 → 3H6) by monitoring the excitation with f–f transition of Pr3+ (3H4 → 3P2) at 449 nm. Emission mechanism in these systems has also been elucidated by an energy level scheme.
    Current Applied Physics 05/2011; 11(3, Supplement):S292-S295. DOI:10.1016/j.cap.2011.01.036 · 2.03 Impact Factor
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    ABSTRACT: The solvothermal synthesis and structural characterization of silicate based oxyapatite activated (CGS) nanophosphors have been reported. The structure of these phosphors was elucidated by the powder x-ray diffraction (XRD) and further characterized by scanning electron microscopy. The XRD results revealed that the obtained shows the characteristic peaks of oxyapatite in a hexagonal lattice structure. The photoluminescence (PL) properties were studied with variations of concentration and sintering temperature. Under excitation, both and characteristic emissions associated with 4f–4f transitions have been observed, and when the concentration of increases above the emission intensity decreases due to cross relaxation. The emission intensity decreases with increasing concentration and the PL intensity of at excitation was much weaker than the obtained intensity with excitation at , suggesting that the efficient energy transfer occurred from to ions in CGS host lattice. The decay curves of the level show that the lifetime decreases with increasing crystallite size and concentration of ions. These luminescent powders are expected to find potential applications such as white light emitting diodes and optical display systems.
    Journal of The Electrochemical Society 01/2011; 158(2):J20-J26. DOI:10.1149/1.3511786 · 2.86 Impact Factor
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    ABSTRACT: The Mesoporous TiO2 hollow spheres are synthesized by a solvothermal reaction without any surfactant and template. The reaction conditions such as reaction temperature, type of precursor, solvent used and their influence on the synthesis of TiO2 hollow spheres are investigated. The synthesized TiO2 hollow spheres are characterized by X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), focused ion beam (FIB) SEM, Barrett-Emmett-Teller (BET) surface areas, and UV-visible diffused reflectance spectroscopy. The synthesized TiO2 spheres have obtained different diameters ranging from 700 nm to 1.79 μm at different reaction temperatures. The shell is composed of numerous single crystalline nanoparticles. The morphology and interiors of the spheres strongly depend upon the experimental parameters such as reaction temperature and a kind of solvent. Especially, interiors of TiO2 hollow spheres such as mesoporous, double shell and single wall structures at various reaction temperatures are discussed with the aid of TEM and FIB SEM measurements.
    Journal of The Electrochemical Society 01/2011; 159(1-1):P8-P13. DOI:10.1149/2.058201jes · 2.86 Impact Factor
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    ABSTRACT: Oxyapatite Ca2Gd8(SiO4)6O2 (CGS) nanostructures with nanorod bundle-like morphology are prepared by mixed solvothermal and hydrothermal reaction methods. Detailed structural and morphological studies are performed using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy measurements. CGS nanorod bundles are formed by crystal splitting, and the growth mechanism as a function of reaction time is discussed. The size and crystal splitting of the nanorod bundles are controlled by varying the concentration of 2-propanol. The annealing temperature does not have any effect on the morphology of CGS nanorod bundles, and the bundles can sustain high temperatures, which confirms the crystal splitting of nanorod bundles. Photoluminescence and cathodoluminescent studies are carried out by activating the Eu3+ ions in the CGS host lattice as a function of annealing temperature. The corresponding CIE chromaticity coordinates are in close proximity to the commercial red emitting phosphor chromaticity coordinates.
    Crystal Growth & Design 01/2011; 12(2-2):960-969. DOI:10.1021/cg2014286 · 4.56 Impact Factor
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    ABSTRACT: We report the properties of upconversion luminescence on Yttrium aluminum perovoskite (YAIO3) doped with trivalent erbium at concentrations of 1, 2, 3, 5 and 7 mol%. The samples were synthesized by solvo-thermal reaction method and the XRD patterns conforms that the YAP:Er(3+) nanophosphors have orthorhombic phase. Efficient green and red upconversion (UC) emission of YAP:Er(3+) nanophosphors was measured under the excitation of 975 nm continuous wave diode laser, and its dynamics and pump power dependence were investigated. As concentration of Er(3+) ion increased from 1 to 7 mol%, the red UC emission increased more rapidly. It is attributed to the energy transfer (4I(11/2) --> 4I(15/2):4I(13/2) --> 4F(9/2)) and to the cross relaxation (4S(3/2) --> 4I(9/2):4I(15/2) --> 4I(13/2)) between Er(3+) ions. In this case, the green and red emissions were yielding from quadratic to linear. These conclusions obtained are confirmed by theoretical investigations based on steady-state rate equations.
    Journal of Nanoscience and Nanotechnology 11/2010; 10(11):7328-32. DOI:10.1166/jnn.2010.2909 · 1.34 Impact Factor
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    ABSTRACT: The synthetic compounds of Sb3+ ion-substituted lanthanide aluminum garnet doped with cerium powders have been prepared by solvothermal method at 230°C and then calcined at 1500°C. These particles have spherical morphology with an average size of about 2 μm, which indicates the good luminescent characteristics. Tb3(SbAl)Al3O12:Ce3+, and Gd3(SbGa)Al3O12:Ce3+ showed not only the red shift but also increased broadness with increased red to green ratio as compared with YAG:Ce3+ phosphor. The color coordination of Ce3+-doped Y3Al2Al3O12, Tb3(SbAl)Al3O12, and Gd3(SbGa)Al3O12 are (0.315, 0.341), (0.332, 0.331), and (0.337, 0.330), respectively. These results demonstrate that the possibility for the use of Tb3(SbAl)Al3O12 and Gd3(SbGa)Al3O12 phosphors to enhance the white light generation in the field of white light-emitting diodes.
    Journal of the American Ceramic Society 10/2010; 94(2):551 - 555. DOI:10.1111/j.1551-2916.2010.04130.x · 2.43 Impact Factor
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    ABSTRACT: A series of Eu3+ ions co-doped (Gd0.9Y0.1)3Al5O12:Bi3+, Tb3+ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet 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 the GYAG:Bi3+, Tb3+, Eu3+ phosphors consists of broad bands in the shorter wavelength region due to 4f8 → 4f75d1 transition of Tb3+ ions overlapped with 6s2 → 6s16p1 (1S0 → 3P1) transition of Bi3+ ions and the charge transfer band of Eu3+–O2−. The present phosphors exhibit green and red colors due to 5D4 → 7F5 transition of Tb3+ ions and 5D0 → 7F1 transition of Eu3+ ions, respectively. The emission was shifted from green to red color by co-doping with Eu3+ ions, which indicate that the energy transfer probability from Tb3+ to Eu3+ ions are dependent strongly on the concentration of Eu3+ ions.
    Solid State Sciences 05/2010; 12:719-724. DOI:10.1016/j.solidstatesciences.2010.02.032 · 1.68 Impact Factor
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    ABSTRACT: Y (10mol%) substituted GAG:Ce (GdYAG:Ce) phosphors have been synthesized by solvothermal reaction method and which were sintered at various temperatures. The XRD patterns confirm that the GdYAG:Ce phosphors have garnet structures with a single cubic phase. GdYAG:Ce phosphors were stable with pure garnet phase at higher temperatures and lower concentration of Y3+ ions. The SEM images of these phosphors show spherical morphology. The luminescent properties of these phosphors have been investigated by the measurement of their emission and excitation spectra. The excitation spectra of GdYAG:Ce phosphors consist of a broad band with a maximum at 485nm and also the emission spectra of these phosphors emit the reddish yellow colors with a peak intensity at 546nm from the measured spectra.
    Optical Materials 12/2009; 32:293-296. DOI:10.1016/j.optmat.2009.08.004 · 2.08 Impact Factor
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    ABSTRACT: Dy3+:GAG nanophosphors have been newly synthesized by solvothermal process. Spherically shaped particles in the nanometer range prepared by this method were evidenced by X-ray diffraction and SEM measurements. The synthesis, structural and luminescent properties along with chromaticity coordinates of the nanophosphor samples with the compositions xDy3+:Gd (1−x)Al5O12 (x=0.5–5mol%) are featured in this paper. Furthermore, the yellow to blue intensity ratio of Dy3+:GAG nanophosphors varies from 0.63 to 0.55. Such luminescent powders are expected to find potential applications such as fluorescent lamps and optical display systems.
    Journal of Alloys and Compounds 07/2009; 481(1):730-734. DOI:10.1016/j.jallcom.2009.03.095 · 2.73 Impact Factor
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    ABSTRACT: Dy3+:GAP (gadolinium aluminum perovskite) powder nanophosphors have been newly synthesized by means of solvothermal process. Spherically shaped particles in the nanometer ranges prepared by this method were evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The synthesis, structural and luminescent properties along with chromaticity coordinates of the nanophosphor samples with the compositions xDy3+:Gd(1−x)AlO3 (x=0.005–0.05) are featured in this paper. Furthermore, the yellow to blue intensity ratio of Dy3+:GAP nanophosphors varies from 1.19 to 1.03. Such luminescent powders are expected to find potential applications such as optical display systems.
    Optical Materials 06/2009; 31:1210-1214. DOI:10.1016/j.optmat.2008.12.015 · 2.08 Impact Factor
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    ABSTRACT: Eu3+ doped Y3Al5O12 (YAG), YAlO3 (YAP) and Y4Al2O9 (YAM) nanophosphors were prepared by solvothermal reaction method. The structural properties were studied by using their XRD measurements and the luminescent properties of these phosphors were investigated by the measurement of their excitation and emission spectra along with their decay curves. The relationship between the structures and the photoluminescence properties of the phosphors has been studied. The emission spectrum of Eu3+ doped YAG phosphor is dominated by orange emission due to 5D0→7F1 transition with inversion symmetry. However, the emission spectrum of Eu3+ doped YAP phosphor is dominated by red emission due to 5D0→7F2 transition without inversion symmetry. The PL spectrum of Eu3+ doped YAM phosphor consists of similar emission intensities for both 5D0→7F1 (590nm) and 5D0→7F2 (607nm) transitions.
    Current Applied Physics 05/2009; 9(3-3, Supplement):S217-S221. DOI:10.1016/j.cap.2009.01.045 · 2.03 Impact Factor
  • Journal- Korean Physical Society 04/2009; 54(4-4):1470-1474. DOI:10.3938/jkps.54.1470 · 0.43 Impact Factor