• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.3
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• pp.216-221
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• 2010

Employing statistical design of experiments, the difference in doping behaviors of rare-earth ions and their effects on the dielectric property and microstructure of $BaTiO_3$-MgO-$MnO_2$-($Ba_{0.4}Ca_{0.6}$) $SiO_3-Re_2O_3$ (Re = $Y_2O_3$, $Er_2O_3$) system were investigated. Through the statistical analysis we have found that the amount of $Re_2O_3$ are significantly affecting on the dielectric properties. The $Re_2O_3$ improved the dielectric constant, dielectric loss and R*C constant, so the appropriate contents of $Y_2O_3$ and $Er_2O_3$ were 0.8 ~ 1.2 mol% and 0.8 ~ 1.3 mol%, respectively. The MLCC(mutilayer chip capacitor) with $2.0{\times}1.2{\times}1.2mm$ size and 475 nF was also suited for X7R with the above composition. It showed that the dielectric constant and RC constant were 2,839 and 3,675 ${\Omega}F$, respectively in the sintering condition at $1250^{\circ}C$ in $Po_2$ $10^{-7}$ Mpa.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1181-1184
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• 2008

$GeO_2$/ormosil organic-inorganic hybrid films doped with neodymium ions and $TiO_2$/Ormosil organic-inorganic hybrid films dispersed with neodymium oxide nanocrystals are prepared by combining an inverse microemulsion technique and a low-temperature sol-gel technique. The effects of $Nd^{3+}$ concentration, $Nd_2O_3$ nanocrystal content, and heat treatment temperature on up-conversion and photoluminescence luminescence properties of the hybrid films are studied.

• Journal of the Korean Chemical Society
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• v.15 no.1
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• pp.5-9
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• 1971

A separation scheme using cation exchange procedure is designed specifically for the rapid determination of thorium in monazite samples. All the coexisting ions in monazite, including rare earth ions, are eluted with 3N hydrochloric acid. The remaining thorium is eluted from the resin column with 5N sulfuric acid prior to spectrophotometric determination with thorin reagent. The radioactive tracers and spectrophotometric methods were used to confirm the quantitative elution of thorium and also the chemical purity of the eluted thorium from the column.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.75-80
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• 2006

We studied feasibility of three-dimensional optical memory by utilizing femtosecond laser-induced changes of transmission in photopolymers and photoluminescence in Eu and Sm ion doped sodium borate glasses. We produced transmission change by two photon absorption and obtained sub-Um size spots in photopolymers using 780 nm modelocked Ti-sapphire laser pulses. We also changed valence state of Eu and Sm ions by multi-photon absorption and achieved $\~{\mu}m$ sized spot formation in Sm-doped glasses.

• Applied Science and Convergence Technology
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• v.23 no.1
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• pp.14-26
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• 2014

Copper is an important component from coin metal to electronic wire, integrated circuit, and to lithium battery. Copper oxides, mainly including $Cu_2O$ and CuO, are important semiconductors for the wide applications in solar cell, catalysis, lithium-ion battery, and sensor. Due to their low cost, low toxicity, and easy synthesis, copper oxides have received much research interest in recent year. Herein, we review the crystallization of copper oxides by designing various chemical reaction routes, for example, the synthesis of $Cu_2O$ by reduction route, the oxidation of copper to $Cu_2O$ or CuO, the chemical transformation of $Cu_2O$ to CuO, the chemical precipitation of CuO. In the designed reaction system, ligands, pH, inorganic ions, temperature were used to control both chemical reactions and the crystallization processes, which finally determined the phases, morphologies and sizes of copper oxides. Furthermore, copper oxides with different structures as electrode materials for lithium-ion batteries were also reviewed. This review presents a simple route to study the reaction-crystallization-performance relationship of Cu-based materials, which can be extended to other inorganic oxides.

• Journal of the Korean Chemical Society
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• v.41 no.11
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• pp.612-638
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• 1997

The methods of separation and recovery of rare earth elements in monazite sand have been studied by the ion exchange chromatography. Both of cation and anion exchange resin were used as ion exchange resins and the solutions of EDTA, DTPA, IMDA and Ln-EDTA were used as eluents. The H+, Zn2+, Fe3+, Al3+, Cu2+, and NH4+ forms of cation exchange resin were used as retaining ions. Ln-EDTA solution was loaded on the EDTA form of anion exchange resin and separated. The Ln-EDTA solution was also used as an eluent for a selective separation of one element from the rare earth mixture solution. The size effects of resin column, the elution mechanism for the various elution types and the separation of a large amount of rare earths were studied.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.170.2-170.2
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• 2015

Enormous interest in trivalent rare-earth (RE) ions activated luminescent materials has been gaining owing to their promising applications in bio-imaging, solar cells, white light-emitting diodes and field-emission displays. Among these trivalent RE ions, dysprosium (Dy3+) was widely investigated due to its unique photoluminescence (PL) emissions. A series of Dy3+-activated CaWO4 phosphors were prepared by a facile high-temperature solid-state reaction method. The X-ray diffraction, PL spectra, cathodoluminescence (CL) spectra as well as PL decay curves were used to characterize the prepared samples. Under ultraviolet light excitation, the characteristic emissions of Dy3+ ions were observed in all the obtained phosphors. Furthermore, the PL emission intensity increased gradually with the increment of Dy3+ ion concentration, reaching its maximum value at an optimized Dy3+ ion concentration. Additionally, color-tunable emissions were obtained in Dy3+-activated CaWO4 system by adjusting the Dy3+ ion concentration and excitation wavelength. Ultimately, strong CL properties were observed in Dy3+-activted CaWO4 phosphors. These results suggested that the Dy3+-activted CaWO4 phosphors may have potential applications in the field of miniature color displays.

• Advances in nano research
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• v.3 no.2
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• pp.55-66
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• 2015

Crystalline $Ce^{3+}$ co-doped $LaPO_4$:RE ($RE=Dy^{3+}$, $Tb^{3+}$, $Eu^{3+}$, $Sm^{3+}$) and mix doped rare earth ions of $Dy^{3+}$, $Tb^{3+}$ and $Eu^{3+}$ were prepared by the polyol method at $150^{\circ}C$. Strongly enhance luminescence intensity is obtained with the co-doping of $Ce^{3+}$ with $LaPO_4$:$Dy^{3+}$ and $LaPO_4$:$Tb^{3+}$ due to charge transfer (CT) occurring from $Ce^{3+}$ to $Dy^{3+}$ and $Ce^{3+}$ to $Tb^{3+}$, where as there is no significant changes in luminescence intensity of $Ce^{3+}$ co-doped $Eu^{3+}$ and $Sm^{3+}$ doped $LaPO_4$ samples. The luminescence color can be tuned from green to white by varying the excitation wavelength for the mix ions $Ce^{3+}$, $Dy^{3+}$, $Tb^{3+}$ and $Eu^{3+}$ doped with $LaPO_4$.

• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.645-652
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• 2019

Phosphor with phosphorus doped with rare earth ions was investigated by searching Sr and Eu phosphors suitable for substitution of Eu ions with similar ionic radius to polyphosphate host. The $NaSr(PO_3)_3$ phosphor was synthesized by the solid state method and the $NaSr(PO_3)_3:Eu^{2+}$ phosphor was prepared by the carbon thermal reduction method. Both of the phosphors were identified by X - ray diffraction. The excitation and emission spectra of $NaSr(PO_3)_3:Eu^{3+}$ increased fluorescence intensity and intensity quenching with increasing $Eu^{3+}$ concentration. The higher the $Eu^{3+}$ concentration in the emission spectrum, the higher the local symmetry of $Eu^{3+}$ environment. The mechanism of concentration quenching, in which fluorescence decreases due to the energy transfer between $Eu^{2+}$ ions with the closest critical distance between $Eu^{2+}$ ions with increasing $Eu^{2+}$ ion concentration, was confirmed in the emission spectrum of $NaSr(PO_3)_3:Eu^{2+}$ concentration. It is possible to change the fluorescent region through the post-processing of single rare earth ion added phosphors, and it is possible to change the fluorescence by applying the energy transfer and concentration quenching mechanism according to the local symmetry of $Eu^{3+}$ will be used for high phosphor development.

• Journal of Environmental Science International
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• v.5 no.2
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• pp.211-220
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• 1996

New thin-and diselena-crown ethers containing two suffer and selenium donor atoms have been prepared. And then, mercury ($Hg^{2+}$) ion-selective electrodes with PVC-plasticizer (STPB) based on some macrocycles as neutral carriers were also made. The electrochemical selectivities for various ions, and the effects for macrocycles, matrix of membranes, ratio of plasticizer to macrowcles, concentration and pH of test solution were investigated on the $Hg^{2+}$ ion-selective electrodes. The 1, 10-diselena-18-crown-6-PVC-STPB (sodium tetraphenylborate) exhibited good linear responses of ${28.2}\pm{0.6}$ decade-1 for $Hg^{2+}$ ion in the conientration ranges of $10^{-2}~10^{-6}$ M $Hg^{2+}$ ion. This electrode exhibited comparatively good selectivities for $Hg^{2+}$ ion in comparison with alkali and alkaline earth metal ions, some heavy metal ions and rare earth metal ion in the range of pH 2.5~6.0. In addition, this electrode was applied as a sensor in the titration of $Hg^{2+}$ ion with $1^-$ ion in water.