• Korean Journal of Materials Research
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• v.27 no.6
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• pp.339-344
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• 2017

A series of $CaNb_2O_6:Dy^{3+}$, $CaNb_2O_6$:$Eu^{3+}$ and $CaNb_2O_6:Dy^{3+}$, $Eu^{3+}$ phosphors were prepared by solid-state reaction process. The effects of activator ions on the structural, morphological and optical properties of the phosphor particles were investigated. XRD patterns showed that all the phosphors had an orthorhombic system with a main (131) diffraction peak. For the $Dy^{3+}$-doped $CaNb_2O_6$ phosphor powders, the excitation spectra consisted of one broad band centered at 267 nm in the range of 210-310 nm and three weak peaks; the main emission band showed an intense yellow band at 575 nm that corresponded to the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transition of $Dy^{3+}$ ions. For the $Eu^{3+}$-doped $CaNb_2O_6$ phosphor, the emission spectra under ultraviolet excitation at 263 nm exhibited one strong reddish-orange band centered at 612 nm and four weak bands at 536, 593, 650, and 705 nm. For the $Dy^{3+}$ and $Eu^{3+}$-codoped $CaNb_2O_6$ phosphor powders, blue and yellow emission bands due to the $^4F_{9/2}{\rightarrow}^6H_{15/2}$ and $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transitions of $Dy^{3+}$ ions and a main reddish-orange emission line at 612 nm resulting from the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ ions were observed. As the concentration of $Eu^{3+}$ ions increased from 1 mol% to 10 mol%, the intensities of the emissions due to $Dy^{3+}$ ions rapidly decreased, while those of the emission bands originating from the $Eu^{3+}$ ions gradually increased, reached maxima at 10 mol%, and then slightly decreased at 15 mol% of $Eu^{3+}$. These results indicate that white light emission can be achieved by modulating the concentrations of the $Eu^{3+}$ ions incorporated into the $Dy^{3+}$-doped $CaNb_2O_6$ host lattice.

• Journal of Magnetics
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• v.17 no.4
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• pp.251-254
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• 2012

The electron paramagnetic resonance (EPR) of the $Eu^{2+}$ ion in $SrCl_2$:Eu single crystal has been investigated using an X-band spectrometer. The angular dependence of magnetic resonance positions for the $Eu^{2+}$ impurity ion in the crystallographic aa-plane is analyzed with effective spin-Hamiltonian. The EPR spectra of the isolated $Eu^{2+}$ center merged to each other. The hyperfine splitting of the isolated $Eu^{2+}$ center due to the $^{151}Eu$ nucleus is approximately 35 G. Three kinds of $Eu^{2+}$ centers except the isolated $Eu^{2+}$ center, $Eu^{2+}$ pairs, $Eu^{2+}$ triples, and other $Eu^{2+}$ clusters, are split from the fitting of the integrated experimental spectrum with the Gaussian curve. The calculated spectroscopic splitting parameters of the $Eu^{2+}$ pairs, $Eu^{2+}$ triples, and other $Eu^{2+}$ clusters in $SrCl_2$:Eu crystal are $g_1$ = 2.06, $g_2$ = 1.94, and $g_3$ = 1.93, respectively.

• Korean Journal of Materials Research
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• v.27 no.2
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• pp.100-106
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• 2017

Nanosized and aggregated $Y_2O_3:Eu$ Red phosphors were prepared by template method from metal salt impregnated into crystalline cellulose. The particle size and photoluminescent property of $Y_2O_3:Eu$ red phosphors were controlled by variation of the calcination temperature and time. Dispersed nanosol was also obtained from the aggregated $Y_2O_3:Eu$ Red phosphor under bead mill wet process. The dispersion property of the $Y_2O_3:Eu$ nanosol was optimized by controlling the bead size, bead content ratio and milling time. The median particle size ($D_{50}$) of $Y_2O_3:Eu$ nanosol was found to be around 100 nm, and to be below 90 nm after centrifuging. In spite of the low photoluminescent properties of $Y_2O_3:Eu$ nanosol, it was observed that the photoluminescent property recovered after re-calcination. The dispersion and photoluminescent properties of $Y_2O_3:Eu$ nanosol were investigated using a particle size analyzer, FE-SEM, and a fluorescence spectrometer.

• Korean Journal of Materials Research
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• v.24 no.9
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• pp.469-473
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• 2014

$SrSnO_3$ phosphor powders were synthesized with two different contents of activator ions $Eu^{3+}$ and $Tb^{3+}$ using the solid-state reaction method. The structural, morphological, and optical properties of the phosphors were investigated using X-ray diffractometry, field-emission scanning electron microscopy, and fluorescence spectrophotometry, respectively. All the phosphors showed a cubic structure, irrespective of the type and the content ratio of activator ions. For $Eu^{3+}$-doped $SrSnO_3$ phosphors, the intensity of the 620 nm red emission spectrum resulting from the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$ was stronger than that of the 595 nm orange emission signal due to the $^5D_0{\rightarrow}^7F_1$ transition in the range 0.01-0.05 mol of $Eu^{3+}$, but the ratio of the intensity was reversed in the range 0.10-0.20 mol of $Eu^{3+}$. The variation in the emission intensity indicates that the site symmetry of the $Eu^{3+}$ ions around the host crystal was changed from non-inversion symmetry to inversion. For the $Tb^{3+}$-doped $SrSnO_3$ phosphors under excitation at 281 nm, one strong green emission band at 550 nm and several weak bands were observed. These results suggest that the optimum red and green emission signals can be realized when the activator ion content for $Eu^{3+}$- or $Tb^{3+}$-doped $SrSnO_3$ phosphors is 0.20 mol and 0.15 mol, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.6
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• pp.527-530
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• 2007

[ $SrTiO_3$ ] red phosphors doped with Pr, Er and Al were synthesized by solid state reaction method. Three emission peaks in photoluminescence spectra of the $SrTiO_3:Eu$ Phosphors were observed at 583 nm, 610 nm and 685 nm. The emission peaks in the $SrTiO_3:Eu$ phosphors were associated with charge-transfer states. The decrease of photoluminescence intensity in $SrTiO_3:Eu,Al$ phosphors with doping Al ions was interpreted by the change of charge-transfer states.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.152-152
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• 2015

최근에 백색 발광체 개발에 많은 관심이 고조되고 있다. 본 연구에서는 고상반응법을 사용하여 활성제 이온 $Dy^{3+}$의 함량을 0.05 mol로 고정하고, $Eu^{3+}$ 이온의 함량을 각각 0, 0.5, 1, 5, 10, 15 mol%로 변화시켜 $Y_2WO_6:Dy^{3+}$, $Eu^{3+}$ 형광체 분말을 합성하였다. $Dy^{3+}$ 이온만 도핑된 $Y_2WO_6$ 형광체의 흡광 수펙트럼은 전하 전달 밴드 ($Dy^{3+}-O^{2-}$)에 의한 250~350 nm에 존재 하는 밴드폭이 넓은 전이 신호와 360~500 nm 영역에 걸쳐 있는 상대적으로 흡광 세기가 약한 다수의 $Dy^{3+}$ 이온의 전이 신호가 관측 되었다. $Dy^{3+}$와 $Eu^{3+}$가 동시 도핑된 $Y_2WO_6$ 형광체의 발광 스펙트럼의 경우에, $Eu^{3+}$ 이온의 몰 비가 증가함에 따라 $Dy^{3+}$ 이온에 의한 577 nm에 주 피크를 갖는 황색 발광 파장의 세기는 감소하였고, $Eu^{3+}$ 이온에 의해 발생하는 612 nm의 적색 발광 파장의 세기는 순차적으로 증가하였다. 이 결과는 $Dy^{3+}$와 $Eu^{3+}$ 이온의 몰 비를 적절히 조절함으로써 최적의 백색 발광 형광체를 제조할 수 있음을 제시한다.

• Journal of the Korean Electrochemical Society
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• v.16 no.3
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• pp.184-189
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• 2013

$Ba_2SiO_4:Eu^{2+}$ ($B_2S:Eu^{2+}$) powders were prepared by firing the dry gel obtained by the sol-gel and the hybrid process (sol-gel and combustion), respectively, and their structure and luminescence were investigated. Tetraethyl orthosilicate (TEOS) was used as a Si source. The phase transition was observed with the TEOS content. With 1.2M TEOS, the powders prepared by the sol-gel process without prior calcination were composed of the $B_2S:Eu^{2+}$ single phase, whereas those by the sol-gel and the hybrid process with prior calcination consisted of the dominant $B_2S:Eu^{2+}$ and minor $BaSiO_3:Eu^{2+}$ ($BS:Eu^{2+}$) phases and their emission intensities were approximately two times higher than those without prior calcination. The hybrid process could reduce the process time innovatively compared to the sol-gel process, even though the former was a little inferior to the latter in the emission intensity of $B_2S:Eu^{2+}$. With 1.1M TEOS, the $B_2S:Eu^{2+}$ single phase was obtained by the hybrid process, and its green emission was observed at 505 nm originated from the $4f^65d^1{\rightarrow}4f^7$ transition of $Eu^{2+}$ ions.

• Journal of Soil and Groundwater Environment
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• v.14 no.4
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• pp.23-32
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• 2009

The sorption of europium (Eu (III)) onto kaolinite and the influence of humic acids over a range of pH 3 ~ 11 has been studied by batch adsorption experiment (V/m = 250 : 1 mL/g, $C_{Eu(III)}\;=\;1\;{\times}\;10^{-5}\;mol/L$, $C_{HA}\;=\;5{\sim}50\;mg/L$, $P_{CO2}=10^{-3.5}\;atm$). The concentrations of HA and Eu(III) in aqueous phase were measured by UV absorbance at 254nm (e.g., $UV_{254}$) and ICP-MS after microwave digestion for HA removals, respectively. Results showed that the HA sorption onto kaolinite was decreased with increasing pH and their sorption isotherms fit well with the Langmuir adsorption model (except pH 3). Maximum amount ($q_{max}$) for the HA sorption at pH 4 to 11 was ranged from 4.73 to 0.47 mg/g. Europium adsorption onto the kaolinite in the absence of HA was typical, showing an increases with pH and a distinct adsorption edge at pH 3 to 5. However in the presence of HA, Eu adsorption to kaolinite was significantly affected. HA was shown to enhance Eu adsorption in the acidic pH range (pH 3 ~ 4) due to the formation of additional binding sites for Eu coming from HA adsorbed onto kaolinite surface, but reduce Eu adsorption in the intermediate and high pH above 6 due to the formation of aqueous Eu-HA complexes. The results on the ternary interaction of kaolinte-Eu-HA are compared with those on the binary system of kaolinite-HA and kaolinite-Eu and adsorption mechanism with pH was discussed.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.02a
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• pp.60-63
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• 2004

Sulfurization of rare-earth oxides R203 (R=Nd, Eu) using sulfurizing reagents, such as $H_2S$ and $SC_2$was examined for the sulfide magnetic separation of spent fuel. $EU_2O_3$was found to react with H$_3$S gas forming the mixture of $EU_2O_2S$ and EuS at 500 oC, while EuS was formed by $SC_2$ at 800 oC. In the case of the mixture of $R_2O_3$and $UO_2$, EuS and $ND_3S_4$ were formed as well as $EU_2O_2S$ and $Nd_2O_2S$ at 500oC in $H_2S$, though $UO_2$ remained unreacted.

• Journal of the Korean institute of surface engineering
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• v.54 no.2
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• pp.96-101
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• 2021

NaNbO₃:Eu³⁺ phosphor thin films were grown on quartz substrates by radio-frequency magnetron sputtering at a growth temperature of 100 ℃, with subsequent annealing at temperatures of 800, 900, and 1000 ℃. The effects of annealing temperature on the structural, morphological, and optical properties of the thin films were investigated. The NaNbO₃:Eu³⁺ sputtering target was synthesized by a solid-state reaction of raw materials Na₂CO₃, Nb₂O₅, and Eu₂O₃. The X-ray diffraction patterns exhibited that the thin films had two mixed phases of NaNbO₃ and Eu₂O₃. Surface morphologies were investigated by using field emission-scanning electron microscopy and indicated that the grains of the thin film annealed at 1000 ℃ showed irregular shapes with an average size of approximately 300 nm. The excitation spectra of Eu³⁺-doped NaNbO₃ thin film consisted of a strong charge transfer band centered at 304 nm in the range of 240-350 nm and two weak peaks at 395 and 462 nm, respectively, resulting from the ⁷F₀→⁵L₆ and ⁷F₀→⁵H₂ transitions of Eu³⁺ ions. The emission spectra under excitation at 304 nm exhibited an intense red band centered at 614 nm and two weak bands at 592 and 681 nm. As the annealing temperature increased from 800 ℃ to 1000 ℃, the intensities of all the emission bands and the band gap energies gradually increased. These results indicate that the higher annealing temperature enhance the luminescent properties of NaNbO₃:Eu³⁺ thin films.