• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.420-420
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• 2012

ZnO seed layer were deposited on quartz substrate by sol-gel method and prism-like Al-doped ZnO nanorods (AZO nanorods) were grown on ZnO seed layer by hydrothermal method with various Al concentration ranging from 0 to 2.0 at.%. Structural and optical properties of the AZO nanorods were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), photoluminescence (PL). The diameter of the AZO nanorods was smaller than undoped ZnO nanorods and its diameter of the AZO nanorods decreased with increasing Al concentration. In XRD spectrum, it was observed that stress and full width at half maximum (FWHM) of the AZO nanorods decreased and the 'c' lattice constant increased as the Al concentration increased. From undoped ZnO nanorods, it was observed that the green-red emission peak of deep-level emission (DLE) in PL spectra. However, after Al doping, not only a broad green emission peak but also a blue emission peak of DLE were observed.

• Journal of Electrochemical Science and Technology
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• 제11권4호
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• pp.411-420
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• 2020

Undesirable interfacial reactions between the cathode and sulfide electrolyte deteriorate the electrochemical performance of all-solid-state cells based on sulfides, presenting a major challenge. Surface modification of cathodes using stable materials has been used as a method for reducing interfacial reactions. In this work, a precursor-based surface modification method using Zr and Mo was applied to a LiNi_0.6Co_0.2Mn_0.2O₂ cathode to enhance the interfacial stability between the cathode and sulfide electrolyte. The source ions (Zr and Mo) coated on the precursor-surface diffused into the structure during the heating process, and influenced the structural parameters. This indicated that the coating ions acted as dopants. They also formed a homogenous coating layer, which are expected to be layers of Li-Zr-O or Li-Mo-O, on the surface of the cathode. The composite electrodes containing the surface-modified LiNi_0.6Co_0.2Mn_0.2O₂ powders exhibited enhanced electrochemical properties. The impedance value of the cells and the formation of undesirable reaction products on the electrodes were also decreased due to surface modification. These results indicate that the precursor-based surface modification using Zr and Mo is an effective method for suppressing side reactions at the cathode/sulfide electrolyte interface.

• 한국재료학회지
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• 제18권4호
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• pp.193-198
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• 2008

$WO_3$-doped $SnO_2$ thin films were prepared in a solution-deposition method and their gas-sensing characteristics were investigated. The doping of $WO_3$ to $SnO_2$ increased the response ($R_a/R_g,\;R_a$: resistance in air, $R_g$: resistance in gas) to $H_2$ substantially. Moreover, the $R_a/R_g$ value of 10 ppm CO increased to 5.65, whereas that of $NO_2$ did not change by a significant amount. The enhanced response to $H_2$ and the selective detection of CO in the presence of $NO_2$ were explained in relation to the change in the surface reaction by the addition of $WO_3$. The $WO_3$-doped $SnO_2$ sensor can be used with the application of a $H_2$ sensor for vehicles that utilize fuel cells and as an air quality sensor to detect CO-containing exhaust gases emitted from gasoline engines.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1432-1433
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• 2006

$Li_{2}CO_3$ doped $Ba_{0.5}Sr_{0.5}TiO_3$ ceramics were fabrication by sol-gel method. Sintering temperature must be suited to the LTCC technology. Structure and dielectric properties were investigated for effect of $Li_{2}CO_3$ dopants at BST. Structure of $Li_{2}CO_3$ doped $Ba_{0.5}Sr_{0.5}TiO_3$ ceramics were dense and homogeneous with almost no pore. Relative permittivity was decreased and dielectric loss was increased with increasing $Li_{2}CO_3$ doping rations. In the case of the 3wt% $Li_{2}CO_3$ doped $Ba_{0.5}Sr_{0.5}TiO_3$ ceramics sintered at $900^{\circ}C$, relative permittivity and dielectric loss were 907 and 0.003 at 100 kHz.

• Bulletin of the Korean Chemical Society
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• 제29권6호
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• pp.1217-1223
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• 2008

A series of Zr,S co-doped $TiO_2$ were synthesized by a modified sol-gel method and characterized by various spectroscopic and analytical techniques. The presence of sulfur caused a red-shift in the absorption band of $TiO_2$. Co-doping of sulfur and zirconium (Zr-$TiO_2$-S) improves the surface properties such as surface area, pore volume, and pore diameter and also enhances the thermal stability of the anatase phase. The Zr-$TiO_2$-S systems are very effective visible-light active catalysts for the degradation of toluene. All reactions follow pseudo firstorder kinetics with the decomposition rate reaching as high as 77% within 4 h. The catalytic activity decreases in the following order: Zr-$TiO_2$-S >$TiO_2$-S >Zr-$TiO_2$>$TiO_2$$\approx$ P-25, demonstrating the synergic effect of codoping with zirconium and sulfur. When the comparison is made within the series of Zr-$TiO_2$-S, the catalytic performance is found to be a function of Zr-contents as follows: 3 wt % Zr-TiO2-S >0.5 wt % Zr-$TiO_2$-S> 5 wt % Zr-$TiO_2$-S >1 wt % Zr-$TiO_2$-S. Higher calcination temperature decreases the reactivity of Zr-$TiO_2$-S.

• 한국세라믹학회지
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• 제44권12호
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• pp.655-659
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• 2007

Zirconia polycrystals co-doped with x mol% CaO and (10-x) mol% $Y_2O_3$ were prepared by solid state reaction method. The compositions were chosen for nominally the same oxygen vacancy concentration of 5 mol%. X-ray diffraction patterns indicated the formation of cubic zirconia by heat treatment at $1600^{\circ}C$. Impedance spectroscopy was applied to deconvolute the bulk and grain boundary response. Electrical conductivity was measured using the complex impedance technique from 516 to 874 K in air. Maximum conductivity was exhibited by the composition with equal amounts of CaO and $Y_2O_3$, which may be ascribed to the smaller degree of defect-interactions in that composition due to the competition of different ordering schemes between the two systems. When compared to the composition containing $Y_2O_3$ only, co-doping of CaO increases the grain boundary resistance considerably. The activation energy of grain and grain boundary conductivity was 1.1 eV and 1.2 eV, respectively, with no appreciable dependence on dopant compositions.

• 한국세라믹학회지
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• 제42권9호
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• pp.602-606
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• 2005

[ $LiCoO_{2}$ ] is the most common cathode electrode materials in Lithium-ion batteries. $LiCo_{0.97}Mg_{0.03}O_2$ was synthesized by the solid-state reaction method. We investigated crystal structures, electrical conductivities and electrochemical properties. The crystal structure of $LiCo_{0.97}Mg_{0.03}O_2$ was analyzed by X-ray powder diffraction and Rietveld refinement. The material showed a single phase of a layered structure with the space group R-3m. The lattice parameter(a, c) of $LiCo_{0.97}Mg_{0.03}O_2$ was larger than that of $LiCoO_2$. The electrical conductivity of sintered samples was measured by the Van der Pauw method. The electrical conductivities of $LiCoO_2$ and $LiCo_{0.97}Mg_{0.03}O_2$ were $2.11{\times}10^{-4}\;S/cm$ and $2.41{\times}10^{-1}\;S/cm$ at room temperature, respectively. On the basis of the Hall effect analysis, the increase in electrical conductivities of $LiCo_{0.97}Mg_{0.03}O_2$ is believed due to the increased carrier concentrations, while the carrier mobility was almost invariant. The electrochemical performance was investigated by coin cell test. $LiCo_{0.97}Mg_{0.03}O_2$ showed improved cycling performance as compared with $LiCoO_2$.

• 한국전기전자재료학회논문지
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• 제18권7호
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• pp.641-646
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• 2005

To fabricate a single layer white organic light emitting diode (OLED), a novel non-conjugated blue emitting material PPPMA-co-DTPM copolymer was synthesized containing a perylene moiety unit with hole transporting and blue emitting ability and a triazine moiety unit with electron transporting ability. The devices were fabricated using PPPMA-co-DTPM $(PPPMA[70\;wt\%]:DTPM[30\;wt\%])$ copolymer by varying the doping concentrations of each red, green and blue fluorescent dye, by molecular-dispersing into Toluene solvent with spin coating method. In case of ITO/PPPMA-co-DTPM:TPB$(3\;mol\%):C6(0.04\;mol\%):NR(0.015\;mol\%)/Al$ structure, as they were molecular-dispersing into 30 mg/ml Toluene solvent, nearly-pure white light was obtained both (0.325, 0.339) in the CIE coordinates at 18 V and (0.335, 0.345) at 15 V. The turn-on voltage was 3 V, the light-emitting turn-on voltage was 4 V, and the maximum external quantum efficiency was $0.667\%$ at 24.5 V. Also, in case of using 40 mg/ml Toluene solvent, the CIE coordinate was (0.345, 0.342) at 20 V.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1613-1618
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• 2014

Perovskite-type oxides are promising oxygen carriers in producing oxygen-enriched $CO_2$ gas stream for oxyfuel combustion. In this study, a new series of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ (x = 0.2, 0.4, 0.6, 0.8) was prepared and used to produce $O_2/CO_2$ mixture gas. The phase, crystal structure, and morphological properties of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ were investigated through X-ray diffraction, specific surface area measurements, and environmental scanning electron microscopy. The oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ was studied in a fixed-bed reactor system. Results showed that the different x values of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ have no obvious effects on crystalline structure. However, the oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ is improved by Co doping. Moreover, $SrCo_{0.8}Fe_{0.2}O_{3-{\delta}}$ synthesized via a new EDTA method has a larger BET surface area ($40.396m^2/g$), smaller particle size (48.3 nm), and better oxygen production performance compared with that synthesized through a liquid citrate method.

• 전기전자학회논문지
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• 제24권3호
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• pp.699-705
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• 2020

본 연구에서는 유기전기발광소자의 전기적 특성을 향상시키기 위한 방법으로, 용액공정 도핑법이 도입된 고분자 poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)] (TFB)기반의 정공수송층을 제안하였다. 정공수송층 소재 TFB 용액 내에 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN)를 3 wt% 도핑을 하여 정공수송층의 전기적 특성을 향상 시켰다. 이를 통해 HAT-CN이 도핑된 TFB을 이용한 유기전기발광소자에서는 향상된 정공수송층의 전도도를 통해 동일 구동 전압 시 전류 밀도와 휘도가 증가하였고, 점등 개시 전압이 13V에서 9V로 줄어드는 것을 확인하였다. 또한, 도핑법이 적용되지 않은 기준 소자 대비 최대 외부양자효율이 3.6%에서 10.8%로 약 3배 향상 되는 것을 확인하였다.