• Analytical Science and Technology
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• v.16 no.3
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• pp.206-211
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• 2003

The DC polarograms of some rare earth elements have been investigated in various pH solution and electrolytes. Samarium ion has two well-defined reduction waves at -1.75 V and -1.95 V in 0.1 M NaCl solution and those are a diffusion controlled in nature. Europium and ytterbium ions give also two step reduction waves at -0.75 V and -1.95 V for europium and -1.45 V and -2.00 V for ytterium in $(C_2H_5)_4NCl$ solution. On the other hand, lantanium and neodium ions show a single reduction wave at -1.75 V. The differences of half wave potentials between europium, ytterium and samarium ions make it possible to determine each ions in the mixed solution sponteniously. In case of europium ion, the stability constants for the complexs of $Eu^{3+}$-EDTA and $Eu^{3+}$-DTPA are evaluated.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.447-453
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• 2011

The monodisperse spherical $SiO_2$ particles were overcoated with $Y_2O_3:Eu^{3+}$ phosphor layers via a Pechini sol-gel process and the resulting $SiO_2@Y_2O_3:Eu^{3+}$ core-shell phosphors were subsequently annealed at $800^{\circ}C$ at an ambient atmosphere. The crystallographic structure, morphology, and luminescent property of core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL). The spherical, nonagglomerated $SiO_2$ particles prepared by a Stober method exhibited a relatively narrow size distribution in the range of 260-300 nm. The thickness of phosphor shell layer in the core-shell particles can be facilely controlled by varying the coating number of $Y_2O_3:Eu^{3+}$ phosphors. The core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors showed a strong red emission, which was dominated by the $^5D_0-^7F_2$ transition (610 nm) of $Eu^{3+}$ ion under the ultraviolet excitation (263 nm). The PL emission properties of $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were also compared with pure $Y_2O_3:Eu^{3+}$ nanophosphors.

• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.261-263
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• 2006

In order to investigate the magnetic properties of Eu ions in the single crystal $MnF_2$, the temperature dependent magnetic susceptibilities of the antiferromagnetic $MnF_2$ and the single crystal $MnF_2$(1.5% $EuF_3$) with the rutile structures were measured in the temperature range from 4K to 300K. The detailed analysis of the measured susceptibilities showed that the magnetic susceptibility by the doping of the small amount $EuF_3$ in the antiferromagnetic single crystal $MnF_2$ follows the antiferromagnetic Curie-Weiss law with the negative paramagnetic Curie temperature similarly as in $MnF_2$. It was also found that Eu ion has +3 valence. This solves the long standing discrepancy on this problem.

• Journal of the Korean Chemical Society
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• v.34 no.6
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• pp.548-554
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• 1990

Temperature effects on the fluorescence emission spectra of 0.01 M Eu(III) ion with ClO$_4$, Cl$^-$, NO$_3$ were studied. Relative intensity change of hypersensitive band ($^5D0\; {\to}\;^7F_2$) and nonhypersensitive band ($^5D0 \;{\to}\;^7F_1$) was quite remarkable with temperature and ligand. The relative intensity change was interpreted as the change of formation constant and used to calculation the enthalpy change of $Eu(H_2O)_X^{3+}$+ to EuL(H$_2O)_{X-1}^{2+}$ complex. $\Delta{H}$ of $Eu(H_2O)_X^{3+}$ to EuCl(H$_2O)_{X-1}^{2+}$ was roughly 15 kJ/mol and temperature independent, but $\Delta{H}$ of EuNO$_3(H_2O)_{X-1}^{2+}$ was changed with temperature; -11 kJ/mol at 25$^{\circ}C$ and 47 kJ/mol at 250$^{\circ}C$.

• Journal of the Korean Chemical Society
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• v.39 no.9
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• pp.705-714
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• 1995

A new analytical luminescence method for the Eu+3 and Tb+3 ions was studied using the luminescence enhancement by the treatment of the o-phenanthroline on the nylon membrane. Compared to the specific emission intensities of the ions in aqueous(or ethanol) solution, if the aqueous ion is spotted on the nylon membrane, the luminescence intensities were extremely enhanced. There was additional enhancement effect of the luminescence intensities of the ions on the nylon membrane, if the ion on the nylon membrane is treated with o-phenanthroline. Based on the luminescence enhancement, the detection limits were lowered by more than 7 order of magnitude compared to that of solution sample, and also lowered by about 1 order of magnitude compared to that of previous TLC method. The dynamic ranges and correlation coefficients of the calibration curves near the detection limit were 2∼3 order and ∼0.99, respectively. It was also shown that the luminescence intensity was in its maximum when the ion on the nylon is treated with ∼4 mole ratio of o-phenanthroline. The energy-transfer mechanism was explained for the theoretical background of the luminescence enhancement.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.91-97
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• 1990

Copolymers (PSAA) of styrene-acrylic acid were prepared through a free radical mechanism using azobisisobutyronitrile as an initiator. The fluorescence emission spectra of PSAA and the styrene-acrylic acid copolymers complexed with $Eu^{3+}$ (PSAA-Eu) were studied. The excimer fluorescence, centered at 330 nm, increases when the styrene mole fraction increases. Since the excimer fluorescence intensities of PSAA-EU, PSAA-Tb and PSAA-Eu-Tb were almost same, it appears that the kind of metal ion does not affect the excimer fluorescence. An interpretation of the results which takes into account the statistical composition of the copolymers, indicates that energy migration can occur from isolated to non-isolated styrene units.

• Journal of the Korean Chemical Society
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• v.39 no.7
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• pp.508-512
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• 1995

A series of samples in the $Eu_{1-x}Sr_xCoO_{3-y}$ system has been prepared by heating the proper amount of reactant mixture to 1150$^{\circ}C$ under an ambient atmosphere, and the solid solutions are identified by X-ray powder diffraction analysis. The crystal system of samples for the compositions of x=0.00 and 0.25 are found to be orthorhombic whose local symmetry is similiar to the distorted octahedra with orthoferrite type one, whereas those of x=0.50 and 0.75 to be the cubic system, and that of x=1.00 to the orthorhombic similiar to be the brownmillerite type. The amount of $Co^{4+}$ ion (${\tau}$ value) is maximized at the composition of x=0.50, and the oxygen vacancies increase with the x value. The nonstoichiometric chemical formula of each compound could be determined from the mole ratio of $Co^{4+}$ ion and oxygen vacancies. The $Co^{3+}$ ion located in octahedral site has spin transition from low spin to high spin states with increasing temperature. Therefore, the effective magnetic moment of each samples obtained from the magnetic measurement is increased with the increasing temperature. The $EuCoO_{3.00}$ has strong antiferromagnetic interaction between the neighboring $Co^{3+}$ ions through the intermediate oxygen ions. With the increasing ${\tau}$ value, the absolute {\theta}_p$ value is decreased by the ferromagnetic interaction of $Co^{3+}-O^2-Co^{4+}$ and thus the {\theta}_p$ has positive value at x=0.50.

• Journal of the Korean Solar Energy Society
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• v.22 no.4
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• pp.44-50
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• 2002

Photosynthesis of plants is effective in the range of 550 to 700 nm of the wavelength of solar irradiation. If the conversion of ultraviolet to the above mentioned region is possible, the photosynthesizing ability is expected to be enhanced. $Eu^{3+}$ doped soda-lime bulk and $TiO_2-SiO_2$ sol-gel coated glasses were prepared and their spectroscopic properties were studied. The absorption and emission spectra for the specimens were measured with the changes of wavelength and Eu ion concentration in the range of the wavelength of 300 to 700nm. The transmittance intensity of visible light through the bulk glass and the coated one was unchanged with the addition of Eu element. The emission spectrum intensity of $Eu^{3+}$ was found to be the maximum at 618 nm which is a transition of $^5DO{\rightarrow}^7F_2$. Additionally, it was shown that the intensity was linearly increased up to 10% of the Eu concentration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.406-407
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• 2008

For this study, Yttrium aluminum garnet (YAG) particles doped $Eu^{3+}$ ions were prepared via the combustion process using the 1:1 ratio of metal ions to reagents. The characteristics of the synthesized nano powder were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and photoluminescence (PL). The various YAG peaks, with the (420) main peak, appeared at all sintering temperature XRD patterns. The YAG phase crystallized with results that are in good agreement with the JCPDS diffraction file 33-0040. The SEM image showed that the resulting YAG:Eu powders had larger sizes with the increse in the sintering temperature. The grain size was about 50nm at $1000^{\circ}C$. The PL intensity of $Eu^{3+}$ has the line peaks of 598, 610, 632nm and has main peak at 591nm.

• Journal of the Korean Vacuum Society
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• v.21 no.2
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• pp.93-98
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• 2012

$Gd_{1-x}VO_4:{Eu_x}^{3+}$ phosphor powders were synthesized with changing the concentration of $Sm^{3+}$ ion by using a solid-state reaction method. The crystal structures of all the phosphors were found to be a tetragonal system, composed of (200) diffraction peak centered at $24.76^{\circ}$, and the morphology of grains approached the spherical form with homeogenous size distribution when the concentration of $Sm^{3+}$ ion was 0.05 mol. As for the photoluminescence properties, all of the phosphor powders, irrespective of $Sm^{3+}$ ion concentration, indicated the yellow, orange, and red emission peaked at 565, 603, and 645 nm respectively. As the concentration of $Sm^{3+}$ ion increases, the intensity of excitation spectrum showed a decreasing tendency on the increase of Sm3+ ion concentration. The maximum excitation and emission spectra were observed and the symmetry ratio was 1.19 at 0.05 mol of $Sm^{3+}$ ion.