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Current Applied Physics 01/2013; 13(3):441-447. · 1.90 Impact Factor
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Journal of the American Ceramic Society 01/2012; 95(1):238-242. · 2.27 Impact Factor
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ABSTRACT: Based on a citric acid-assisted hydrothermal method, series of Ce3+/Tb3+ activated fluorides have been synthesized. By controlling the amount of KNO3, the final products evolve from the Ce3+/Tb3+ codoped orthorhombic phase GdF3 to the Ce3+/Tb3+ codoped cubic phase KGdF4. The concentration of Ce3+ has great effects on the crystalline phases and the morphologies of final products. The Ce3+ concentration dependent samples illustrate the appearance of the hexagonal phase solid solution CeF3–GdF3–TbF3 in the final products. When the Ce3+ concentration is 20 mol%, the sample Ce20 presents the hexagonal phase CeF3 but the diffraction peaks move to higher degree. The x-ray diffraction patterns suggest the phase evolution of final products, the field emission scanning electron microscopy images present the variation in morphology of samples, and the photoluminescence excitation and emission spectra as well as the luminescent dynamic curves illustrate the optical properties of samples.
Journal of Materials Research. 12/2011; 26(23):2916 - 2923.
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ABSTRACT: Lu(6)WO(12) and Lu(6)MoO(12) doped with Eu(3+) ions have been prepared by using a citrate complexation route, followed by calcination at different temperatures. The morphology, structure, and optical and photoluminescence properties of the compounds were studied as a function of calcination temperature. Both compositions undergo transitions from a cubic to a hexagonal phase when the calcination temperature increases. All the compositions have strong absorption of near-UV light and show intense red luminescence under a near-UV excitation, which is related to the transfer of energy from the host lattices to dopant Eu(3+) ions. Density functional theory calculations have also been performed. The calculation reveals that hexagonal Lu(6)WO(12) and Lu(6)MoO(12) are indirect bandgap materials, and the near-UV excitations are due to the electronic transitions from the O-2p orbitals to W-5d and Mo-4d orbitals, respectively. The lattice parameters and bandgap energies of hexagonal Lu(6)WO(12) and Lu(6)MoO(12) were determined.
Inorganic Chemistry 11/2011; 50(24):12522-30. · 4.60 Impact Factor
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Integrated Ferroelectrics 10/2011; 79(2006):71-79. · 0.30 Impact Factor
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ABSTRACT: In display applications, each displays technique needs different phosphors according to its applications. So, in this paper, nano-sized red emitting CaTiO3:Pr3+ powder phosphors were prepared by solvothermal reaction method. The phase purity and the structure of the phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM). The particles show the spherical morphology, which indicates the good luminescent characteristics. The luminescent properties of CaTiO3:Pr3+ powder phosphors have been carried out by the measurement of their phototluminescence (PL) and phototluminescence excitation (PLE) spectra. The PL spectra shows the strong red emission due to 1D2 --> 3H4 transition. The emissions of intra-4f transitions from the excited states (1D2) to the ground state (3H4) of Pr3+ are mainly observed around from 612 to 618 nm. The effect of the Pr3+ concentration on their photoluminescent properties was investigated extensively. These luminescent powders are expected to find potential applications such as optical display systems.
Journal of Nanoscience and Nanotechnology 07/2011; 11(7):6208-12. · 1.56 Impact Factor
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ABSTRACT: 2 mol% Dy3+-doped NaYF4 microcrystals with different morphologies and crystalline phases have been synthesized through a hydrothermal method without assistance of any surfactant, catalyst, or template by controlling reaction temperatures, reaction time, and molar ratios of reactants. For comparison, the samples were also synthesized by a direct coprecipitation method. The final products were characterized by X-ray diffraction, field emission scanning electron microscopy, photoluminescence excitation and emission spectra, and luminescent dynamic decay curves. Dy3+ exhibits bright white light under near ultraviolet 350 or 351 nm excitation and the white light was evaluated by chromaticity coordinates. The experimental results suggest that the obtained Dy3+-doped NaYF4 microcrystals have potential applications in white light materials.
Journal of the American Ceramic Society 04/2011; 94(10):3405 - 3411. · 2.27 Impact Factor
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ABSTRACT: Hexagonal monodisperse NaCeF(4) and NaCeF(4):Tb(3+) nanorods have been successfully synthesized by a polyol-mediated solvothermal route with ethylene glycol (EG) as solvent. The crystalline phase, size, morphology, and luminescence properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra as well as dynamic decays. The experimental results indicate that the content of NH(4)F and NaNO(3) are crucial in controlling product morphology and size. Nanorods with different aspect ratios could be controllably obtained under settled conditions. Shape-dependent luminescence and energy transfer routes from Ce(3+) to Tb(3+) in NaCeF(4):Tb(3+) nanorods were observed by the modified local crystal field environment around rare earth ions. The 4f-5d transitions of Ce(3+) ions have much higher sensitivity to the anisotropic shape of samples than that of Tb(3+) ions.
Inorganic Chemistry 03/2011; 50(8):3387-93. · 4.60 Impact Factor
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ABSTRACT: In this paper, CaSnO3:Eu3+ nanocrystals were prepared by hydrothermal synthesis method. The influence of different molar ratio of Ca:Sn on structure of CaSnO3:Eu3+ was investigated by using X-ray powder diffraction (XRD). Well-crystallized and phase-pure CaSnO3:Eu3+ particles of approximately 90 nm in size can be readily obtained at 900 degrees C. Furthermore, photoluminescence characterization of the Eu(3+)-doped CaSnO3 nanocrystals was performed and discussed. The emission peak situated at 618 nm showing prominent and bright red light is due to the 5D0-7F2 electric dipole transition. The excellent luminescence properties make it possible as a good candidate for PDP application.
Journal of Nanoscience and Nanotechnology 02/2011; 11(2):1629-31. · 1.56 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.
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Journal of Alloys and Compounds 01/2011; 509(27):7537-7542. · 2.29 Impact Factor
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Crystal Growth & Design 01/2011; 12(2):960-969. · 4.72 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 01/2011; 21(17):6136-6139. · 5.97 Impact Factor
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Current Applied Physics 01/2011; 11(3, Supplement):S292-S295. · 1.90 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):P8-P13. · 2.59 Impact Factor
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ABSTRACT: Eu(3+)-doped tetragonal and monoclinic ZrO2 (called t-ZrO2:Eu and m-ZrO2:Eu, respectively) nanoparticles were prepared using the Pechini sol-gel process. The samples were characterized via X-ray diffraction (XRD) and field-emission-scanning electron microscopy (FE-SEM), and with photoluminescence spectra. The influences of the Eu3+ concentration and the fired temperature on the crystal phase composition of the tetragonal and monoclinic ZrO2:Eu were reported. The typical interesting photoluminescence (PL) properties of the t-ZrO2:Eu and m-ZrO2:Eu nanoparticles were presented. In the t-ZrO2:Eu and m-ZrO2:Eu, the main emission peaks were at 607 and 615 nm, respectively, both of which originated from the 5D0-7F2 transition. The excitation band of the t-ZrO2:Eu powder with a lower Eu3+ doping concentration that was obtained at a low temperature (450 degrees C) consisted of a broad band of 230-500 nm. Both broad excitation bands in the t-ZrO2:Eu and m-ZrO2:Eu were ascribed to the O(2-) - Eu3+ charge transfer (CT) transition. The reason was discussed based on the relationship between the CT energy and its crystal structure. The CT energy of m-ZrO2:Eu is higher than that of t-ZrO2:Eu. A detailed chemical bond analysis was performed to explore the CT energy difference between t-ZrO2: Eu and m-ZrO2:Eu.
Journal of Nanoscience and Nanotechnology 01/2011; 11(1):350-7. · 1.56 Impact Factor
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ABSTRACT: Europium-doped nanosized-GdVO4:Eu3+ powders and bulk GdVO4:Eu3+ powders were synthesized using a planetary ball mill and conventional solid state reaction method, respectively. The effects of the grain size on the crystallinity, morphology, structure and luminescence spectra were investigated by X-ray diffraction, field emission-scanning electron microscopy and photoluminescence spectroscopy (PL). The room temperature PL spectra of the GdVO4:Eu3+ nanophosphors showed four emission bands at 611, 615, 619 and 595 nm. The bands at 611, 615 and 619 nm were assigned to the 5D0 --> 7F2 transition of the EU3+ ion when excited with 312 nm light.
Journal of Nanoscience and Nanotechnology 01/2011; 11(1):474-8. · 1.56 Impact Factor
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ABSTRACT: Novel green-light-emitting Tb(3+)-doped SrZnO2 phosphor thin films were grown via the pulsed-laser-deposition technique. The films were grown at various substrate temperatures and oxygen pressures. The crystallinity and surface morphology of the films were investigated via X-ray diffraction (XRD) and atomic-force microscopy (AFM), respectively. The luminescence properties were analyzed by measuring the excitation and photoluminescence spectra. The thin films showed a green emission radiated by the transitions from the 5D4 excited states to the 7FJ (J = 3-6) ground states of the Tb3+ ions found under ultraviolet excitation with a 272 nm wavelength. The crystallinity, surface morphology, and photoluminescence spectra of thin-film phosphors were found to be highly dependent on the deposition conditions, particularly the substrate temperature and oxygen pressure. The surface roughness and photoluminescence intensity of the films showed similar behaviors as a function of the substrate temperature and oxygen pressure.
Journal of Nanoscience and Nanotechnology 01/2011; 11(1):871-5. · 1.56 Impact Factor
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ABSTRACT: Eu3+-doped Gd2O3 inverse opal photonic crystals were successfully synthesized based on a self-assembly technique and a sol−gel method. The inverse opal Gd2O3:Eu3+ material exhibited a pronounced photonic stop band in the visible region. The effect of the stop band on the spontaneous emission of Eu3+ has been studied. Significant suppression of the emission was observed when the Eu3+ ions’ emission bands overlapped with the photonic stop band, whereas enhancement of the emission intensity was detected when the emission bands appeared at the long wavelength edge of the band gap.
11/2010;
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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. · 1.56 Impact Factor
