• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.246-249
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• 2005

The blue-color emitting phosphor powder, $CaMgSi_{2}O_6:Eu^{2+}(CMS:Eu^{2+})$ was synthesized by the solid-state reaction method. The synthesized powder was annealed from room temperature to $1,100^{\circ}C$ in air. Its PL property and valence state of Eu atoms was measured by the photoluminescence (PL) and the electron paramagnetic resonance (EPR) spectrometers, respectively. The PL intensity was stable to $700^{\circ}C$, but drastically decreased to $1,100^{\circ}C$. The behavior of EPR intensity was very similar to the PL intensity. The EPR measurement showed that decreased intensity of the PL was caused to the oxidation from the ion $Eu^{2+}$ to $Eu^{3+}$ ions. The EPR spectrometer was powerful as a tool that could distinguish between the valence states of Eu atom as a dopant in various phosphors.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1859-1864
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• 2011

Two lanthanide complexes, $[Ln(NO_3)_2(H_2O)_3(L)_2](NO_3)(H_2O)$ {Ln = Eu (1), Tb (2); L = 2-(4-pyridylium)-ethanesulfonate, $(4-pyH)^+-CH_2CH_2-SO_3^-)$}, were prepared from lanthanide nitrate and 4-pyridineethanesulfonic acid in $H_2O$ under microwave-heating conditions. Complexes 1 and 2 are isostructural, and the lanthanide metal in both complexes is coordinated to nine oxygen atoms. The pyridyl nitrogen in the ligand is protonated to give a zwitter ion that possesses an $NH^+$ (pyridyl) positive end and an $SO_3^-$ negative end. All O-H and N-H hydrogen atoms participate in hydrogen bonds to generate a two-dimensional (complex 1) or a three-dimensional network (complex 2). Complex 1 exhibits an intense red emission, whereas complex 2 exhibits an intense green emission in the solid state at room temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.4
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• pp.195-200
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• 2013

Novel Sr-Y-Si-Oxynitride yellow phosphors were synthesized and the effect of calcination temperature, reduction temperature and $Eu^{2+}$ concentration on their luminescence properties were studied. Optimal temperature conditions were found to be $1400^{\circ}C$ and $1300^{\circ}C$ for solid-state reaction and reduction, respectively. The synthesized $Ba_9Y_{2+y}Si_6O_{24-3y}N_{3y}:Eu^{2+}$ phosphors showed a single intense broadband emission in the range of 571~587 nm for 450 nm excitation light source. The highest luminescence intensity was obtained with Eu concentration of 3 mol% and concentration quenching was observed beyond 5 mol%. FE-SEM and PSA showed that the synthesized phosphors consists of particles with an average size of ${\sim}8.2{\mu}m$.

• Imaging Science in Dentistry
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• v.31 no.1
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• pp.1-7
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• 2001

Purpose : To evaluate the usefulness of the reconstructed 3-dimensional image on the personal computer in comparison with that of the CT workstation by quantitative comparison and analysis. Materials and Methods : The spiral CT data obtained from 27 persons were transferred from the CT workstation to a personal computer, and they were reconstructed as 3-dimensional image on the personal computer using V-works 2.0/sup TM/. One observer obtained the 14 measurements on the reconstructed 3-dimensional image on both the CT workstation and the personal computer. Paired Nest was used to evaluate the intraobserver difference and the mean value of the each measurement on the CT workstation and the personal computer. Pearson correlation analysis and % incongruence were also performed. Results: I-Gn, N-Gn, N-A, N-Ns, B-A, and G-Op did not show any statistically significant difference (p>0.05), B-O, B-N, Eu-Eu, Zy-Zy, Biw, D-D, Orbrd R, and L had statistically significant difference (p<0.05), but the mean values of the differences of all measurements were below 2 mm, except for D-D. The value of correlation coefficient y was greater than 0.95 at I-Gn, N-Gn, N-A, N-Ns, B-A, B-N, G-Op, Eu-Eu, Zy-Zy, and Biw, and it was 0.75 at B-O, 0.78 at D-D, and 0.82 at both Orbrd Rand L. The % incongruence was below 4% at I-Gn, N-Gn, N-A, N-Ns, B-A, B-N, G-Op, Eu-Eu, Zy-Zy, and Biw, and 7.18%, 10.78%, 4.97%, 5.89% at B-O, D-D, Orbrd Rand L respectively. Conclusion : It can be considered that the utilization of the personal computer has great usefulness in reconstruction of the 3-dimensional image when it comes to the economics, accessibility and convenience, except for thin bones and the landmarks which are difficult to be located.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.54-54
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• 2008

$Eu^{2+}$, $Nd^{3+}$ co-doped $BaAl_2O_4$ are known as a long afterglow phosphor. We found that $Eu^{2+}$-doped $BaAl_2O_4$ showed ptotoconductivity in the range of UV and visual light. In this study, $BaAl_2O_4$:Eu thin film has been prepared by RF sputtering method and a sensing characteristics to UV and visual light was performed. Only $Eu^{2+}$ and $Nd^{3+}$ co-doped $BaAl_2O_4$ powders and targets for deposition were prepared by a convention solid state method, and the deposition was performed in a reducing $H_2$-Ar mixture gas on Si substrates. The observation of crystalline phase and morphology of the sputtered film were performed using XRD, EDX. The photoluminescence and photocurrent to UV and visual light were measured simultaneously using 300W-Xe solar simulator as a light source. It was confirmed that the photocurrent induced by irradiation of light showed a linear relationship to the light intensity.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.59-66
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• 1992

To develop the highly sensitive TLD radiation sensors, $BaSO_{4}$ : Eu-PTFE TLDs are fabricated by polymerizing the PTFE(polytetrafluoroethylene) with $BaSO_{4}$ : Eu TL phosphors. The $BaSO_{4}$ : Eu TL phosphors having the highest sensitivity of $X/{\gamma}$-rays are obtained by sintering at $1000^{\circ}C$ in $N_{2}$ atmosphere a mixture of $BaSO_{4}$ powder with 1mol% Eu($Eu_{2}O_{3}$), 6mol% $NH_{4}Cl$ and 5mol% $(NH_{4})_{2}SO_{4}$ which were co-precipitated in dilute sulfuric acid and then dried. The activation energy, frequency factor and kinetic order of $BaSO_{4}$ : Eu TL phosphor are 1.17eV, $3.6{\times}10^{11}/sec$ and 1.25, respectively. And the spectral peak of $BaSO_{4}$ : Eu is about 425nm. The optimum TL Phosphor content and thickness of the $BaSO_{4}$ : Eu-PTFE TLD are 40wt% and $105.7mg/cm^{2}$. The optimum polymerization temperature and time for fabrication of $BaSO_{4}$ : Eu-PTFE TLDs are $380^{\circ}C$ and 2 hours in air, respectively. The linear dose range to ${\gamma}$ rays is 0.01-20Gy and fading rate is about 10%/60hours.

• Journal of the Korean Society of Visualization
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• v.17 no.3
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• pp.59-65
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• 2019

Phosphor particles ((Sr,Mg)₂ SiO₄:Eu²⁺ were suspended in deionized water in quartz cuvette and used for measuring liquid temperature field by using two-color-ratio method. In the temperature range of 23~77℃, it showed the relative error from 2.4% to 4% and the temperature sensitivity of 0.65 %/℃ at 30℃ and 0.95 %/℃ at 77 ℃. This performance is comparable to measurement techniques using thermographic liquid crystal or laser induced fluorescence or other thermographic phosphor particle. Among investigated potential error sources, the particle number density affected the intensity ratio and the temperature, but the effect of laser fluence was not evident.

• Bulletin of the Korean Chemical Society
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• v.35 no.11
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• pp.3319-3325
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• 2014

Eu(III)-doped $CeO_2$ nanorods were prepared by a co-precipitation method at room temperature, and their photoluminescence profiles were examined with different Eu(III)-doping concentrations and thermal annealing temperatures. Scanning electron microscopy, X-ray diffraction crystallography and UV-Vis absorption spectroscopy were employed to examine the morphology, crystal structure and photon absorption profiles of the nanorods, respectively. Additionally, their 2D and 3D-photoluminescence profile maps were obtained to fully understand the photoluminescence mechanism. We found that the magnetic dipole $^5D_0{\rightarrow}^7F_1$ and the electric dipole $^5D_0{\rightarrow}^7F_2$ transitions of Eu(III) were highly dependent on the doping concentration, annealing temperature and excitation wavelength, which was explained by the presence of different Eu(III)-doping sites (with and without an inversion center) in the $CeO_2$ host with a cubic crystal structure.

• Journal of the Korean Ceramic Society
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• v.47 no.2
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• pp.177-182
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• 2010

To synthesize $Gd_2O_3:Eu^{3+}$ phosphor, gadolinium-europium oxalate precursors were prepared from oxalic acid, NaOH or aqueous ammonia via coprecipitation method. The obtained precursors were heat-treated and then characterized by XRD, SEM and PL. The kinds and amounts of coprecipitant (NaOH or aqueous ammonia) were found to affect the powder morphology and properties of gadolinium-europium oxalate precursors. Two crystalline precursors and one amorphous precursor were synthesized. The nanometer-sized amorphous gadolinium-europium oxalate precursor was first prepared using the oxalate coprecipitation technique. The calcined powders obtained from the amorphous precursor were nearly spherical in shape, and a narrow size distribution was obtained. The NaOH coprecipitant was more effective in the preparation of nanometer-sized spherical powders. A thermal decomposition process was conducted for the three kinds of precursors. The photoluminescence property was also measured as a function of europium content, and concentration quenching occurred for samples with europium concentrations of over 10 mol%.

• Korean Journal of Materials Research
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• v.14 no.10
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• pp.749-753
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• 2004

In this study, we attempt to synthesize the $Sr_{3}SiO_{5}:Eu$ yellow phosphor by sol-gel technique. Based on the blue emitting diodes as primary light source, white light emitting diodes have been manufactured using the $Sr_{3}SiO_{5}:Eu$ yellow phosphor as the luminescent material. Luminescent efficiency of yellow phosphor as well as that of blue LED is very important factor to enhance the luminescent efficiency of white LED. In order to improve the luminescent efficiency, we have synthesized the $Sr_{3}SiO_{5}:Eu$ phosphor by sol-gel technique. To research optimum condition of gelation reaction, the ratio of $H_{2}O$ to TEOS was fixed as 60:1. When the drying temperature was at $100^{\circ}C$, emission intensity was better than at $70^{\circ}C$. The critical $Eu^{2+}$ concentration was estimated to be about 0.05 mol and sintering temperature at $1300^{\circ}C$ was indicated best emission intensity.