• 한국재료학회지
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• 제22권4호
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• pp.207-210
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• 2012

The preparation of $Sm_2O_3$ doped $CeO_2$ in Igepal CO-520/cyclohexane reverse micelle solutions has been studied. In the present work, we synthesized nanosized $Sm_2O_3$ doped $CeO_2$ powders by reverse micelle process using aqueous ammonia as the precipitant; hydroxide precursor was obtained from nitrate solutions dispersed in the nanosized aqueous domains of a micro emulsion consisting of cyclohexane as the oil phase, and poly (xoyethylene) nonylphenylether (Igepal CO-520) as the non-ionic surfactant. The synthesized and calcined powders were characterized by Thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), and Transmission electron microscopy (TEM). The crystallite size was found to increase with increase in water to surfactant (R) molar ratio. Average particle size and distribution of the synthesized $Sm_2O_3$ doped $CeO_2$ were below 10 nm and narrow, respectively. TG-DTA analysis shows that phase of $Sm_2O_3$ doped $CeO_2$ nanoparticles changed from monoclinic to tetragonal at approximately $560^{\circ}C$. The phase of the synthesized $Sm_2O_3$ doped $CeO_2$ with heating to $600^{\circ}C$ for 30 min was tetragonal $CeO_2$. This study revealed that the particle formation process in reverse micelles is based on a two step model. The rapid first step is the complete reduction of the metal to the zero valence state. The second step is growth, via reagent exchanges between micelles through the inter-micellar exchange.

• 한국전기전자재료학회논문지
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• 제16권11호
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• pp.979-986
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• 2003

Sintering behavior and electrical properties of CeO$_2$ system were investigated as a function of the amount of Gd:$_2$O$_3$, and Sm$_2$O$_3$, addition. Doped CeO$_2$ consisted of a homogeneous solid solution of the cubic fluorite structure within the amount of addition from 0 mol% to 15 mol%. Grain growth rate of Gd$_2$O$_3$-doped CeO$_2$ was much smaller than that of pure CeO$_2$, while densification rate was considerably larger. Thus doped CeO$_2$ showed a higher density than pure CeO$_2$. The electrical conductivity of Ce$_1$-$_{x}$Sm$_{x}$O$_1$-$_{x}$/2 was increased up to x = 0.2. However, with further increasing dopant concentrations, the magnitude of the conductivity was found to decrease remarkably. The ionic conductivity value obtained at $700^{\circ}C$ for 10 mol% Sm$_2$O$_3$-doped CeO$_2$ electrolyte was 4.6${\times}$10$^{-2}$ S$.$$cm^{-1}$ /.EX> /.

• 한국세라믹학회지
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• 제35권4호
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• pp.355-363
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• 1998

The oxygen flux of SDC ($Sm_2O_3\;doped\;CeO_2$) solid electrolyte membranes with electronic and oxygen ion-ic conductivities has been investigated as a basic research in order to develop the conversion process of na-tural gas to syngas using the ceramic membrane reactor. Tube type membranes(1 mm thickness) were fa-bricated by slip casting of SDC powders prepared by the oxalate coprecipitaion method. Dense oxygen per-meation membranes(0.1 mm thickness) could be synthesized via sintering at $1450^{\circ}C$ for 2h and their re-lative density was over 95% The oxygen flux through SDC membranes doped 20mol% $Sm_15$ was about $1.13{\times}10^{-5}\;mol/m_2{\cdot}sec$ at low temperature around $800^{\circ}C$. In addition the SDC membranes showed a good thermaal stability for a long period of service.

• 한국세라믹학회지
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• 제53권5호
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• pp.500-505
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• 2016

Scandia-stabilized zirconia co-doped with $CeO_2$ is a promising electrolyte for intermediate temperature SOFC, but still shows rapid degradation during a long-term operation. In this study, $CeO_2$ (1 mol%) as a stabilizer is partially substituted with lanthanum oxides ($M_2O_3$, M=Yb, Gd, Sm) to stabilize a cubic phase and thus durability in reducing atmosphere. 0.5M0.5Ce10ScSZ electrolytes were prepared by solid state reaction and sintered at $1450^{\circ}C$ for 10 h to produce dense ceramic specimens. With addition of the lanthanum oxide, 0.5M0.5Ce10ScSZ showed lower degradation rates than 1Ce10ScSZ. Since $Gd_2O_3$ showed the highest ionic conductivity among the co-dopants, an electrolyte-supported cell with 0.5Gd0.5Ce10ScSZ was prepared to compare its long-term performance with that of 1Ce10ScSZ-based cell. Maximum power density of 0.5Gd0.5Ce10ScSZ-based cell was degraded by about 2.3% after 250 h, which was much lower than 1Ce10ScSZ-based cell (4.2%).

• 한국세라믹학회지
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• 제45권12호
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• pp.766-771
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• 2008

We fabricated single cells with a cathode consisting of a $LaNi_{0.6}Fe_{0.4}O_3-Ce_{0.8}Sm_{0.2}O_{1.9}$ composite (LNF-S20DC composite) active layer and an LNF current collecting layer on a ${0.89ZrO_2}-{0.10Sc_2}{O_3}-0.01{Al_2}{O_3}$ electrolyte sheet. The cathode layers were prepared by the screen-printing method. The cathode properties of these cells were measured by the AC impedance method at $800^{\circ}C$. The cathodes with the ceria-LNF composite active layer exhibited high power performance prior to current loading. We investigated the influence of the mixture ratio of LNF and S20DC on the cathodes properties. The Sm in the ceria particles of the composite cathode was substituted with other rare-earth elements. Cathodes with Pr and Gd co-doped ceria in the active layer provided the better performance than those with Sm- or Gd-doped ceria.

• 한국세라믹학회지
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• 제37권7호
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• pp.705-712
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• 2000

In this study, the dispersion stability of CeO2 based complex oxide was studied, and density, porosity, and microstructure of green body were investigated using colloid surface chemistry to manufacture the Gd2O3 doped CeO2 solid electrolyte in an aqueous system. To prepare the stable slurry for slip casting, the dispersion stability was examined as a function of pH using ESA(electrokinetic sonic anplitude) analysis. The dynamic mobility of particles was enhanced with anionic and cationic dispersant were added the amount of 0.5wt% respectively, but pH value in slurries didn't move to below 6.0 because of the influence of dopants. This phenomenon also appeared in the CeO2-Y2O3 and CeO2-Sm2O3 systems, so it could be inferred that rare earth dopants such as Gd2O3, Sm2O3 and Y2O3 not only have the similar motion with changing pH in an aqueous system but also can be dissolved in the range of pH 6.0∼6.5. In CeO2-Gd2O3 system, when the anionic dispersant was added the amount of 0.5wt% and pH value in slurries was fixed at 9.5, the green body density was 4.07g/㎤, and the relative density of sintered body was 95.2%. It could be inferred from XRD analysis that Gd3+ substituted into Ce4+ site because there was no free Gd2O3 peak.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.187-195
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• 2018

$Sr_{0.92}Y_{0.08}Ti_{1-x}Ni_xO_{3-{\delta}}$ (SYTN) was investigated in the presence of $H_2S$ containing fuels to assess the feasibility of employing oxide materials as alternative anodes. Aliovalent substitution of $Ni^{2+}$ into $Ti^{4+}$ increased the ionic conductivity of perovskite, leading to improved electrochemical performance of the SYTN anode. The maximum power densities were 32.4 and $45.3mW/cm^2$ in $H_2$ at $900^{\circ}C$ for the SYT anode and the SYTN anode, respectively. However, the maximum power densities in 300 ppm of $H_2S$ decreased by 7% and by 46% in the SYT and the SYTN anodes, respectively. To enhance the sulfur tolerance and to improve the electrochemical properties, the surface of SYTN anode was modified with samarium doped ceria (SDC) using the sol-gel coating method. For the SDC-modified SYTN anode, the cell performance was mostly recovered in the pure $H_2$ condition after 500-ppm $H_2S$ exposure in contrast to the irreversible cell performance degradation exhibited in the unmodified SYTN anode.

• 전기화학회지
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• 제14권3호
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• pp.176-183
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• 2011

본 연구에서는 Sr이 치환된 이중층 페로브스카이트($SmBa_{0.5}Sr_{0.5}Co_2O_{5+{\delta}}$, SBSCO)와 전해질 물질로 사용되는 $Ce_{0.9}Gd_{0.1}O_{2-{\delta}}$ (CGO91)을 기반으로 한 중 저온형 고체산화물 연료전지 (ITSOFC) 복합공기극의 분말 크기와 열 사이클에 대한 전기화학특성을 연구하였다. 복합공기극의 모체가 되는 SBSCO에 CGO91물질을 이용하여 면적비저항을 확인 한 결과 약 $0.54\sim9.04{\mu}m$의 분말 크기를 보이는 SBSCO와 $0.4\sim42{\mu}m$의 분말 크기를 보인 CGO91이 각각 50 wt%로 구성된 SBSCO : 50 복합공기극이 600 및 $700^{\circ}C$에서 약 0.102 및 $0.013{\Omega}cm^2$의 우수한 면적비 저항을 가지는 것을 확인 하였으며 상대적으로 분말 크기가 큰 CGO91 분말을 이용한 두 개의 공기극의 경우 $700^{\circ}C$에서 약 $0.260{\Omega}cm^2$와 $0.055{\Omega}cm^2$의 특성을 보여주었다. 10회에 걸친 열 사이클실험을 통하여 SBSCO : 50의 면적비저항은 $0.0193{\Omega}cm^2$에서 $0.094{\Omega}cm^2$로 증가하였으며 7회 이후의 면적비저항은 일정하게 유지됨을 확인하였다.

• Journal of Electrochemical Science and Technology
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• 제10권3호
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• pp.335-343
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• 2019

In this study, $Sr_2Ni_{1.8}Mo_{0.2}O_{6-{\delta}}$ (SNM) with a double perovskite structure was investigated as an alternative anode for use in the $CH_4$ fuel in solid oxide fuel cells. SNM demonstrates a double perovskite phase over $600^{\circ}C$ and marginal crystallization at higher temperatures. The Ni nanoparticles were exsolved from the SNM anode during the fabrication process. As the SNM anode demonstrates poor electrochemical and electro-catalytic properties in the $H_2$ and $CH_4$ fuels, it was modified by applying a samarium-doped ceria (SDC) coating on its surface to improve the cell performance. As a result of this SDC modification, the cell performance improved from $39.4mW/cm^2$ to $117.7mW/cm^2$ in $H_2$ and from $15.9mW/cm^2$ to $66.6mW/cm^2$ in $CH_4$ at $850^{\circ}C$. The mixed ionic and electronic conductive property of the SDC provided electrochemical oxidation sites that are beyond the triple boundary phase sites in the SNM anode. In addition, the carbon deposition on the SDC thin layer was minimized due to the SDC's excellent oxygen ion conductivity.