• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.143.2-143
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• 2000

• The Korean Journal of Ceramics
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• v.7 no.2
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• pp.93-96
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• 2001

The Y- or Yb-doped SrZrO$_3$ proton conductors were fabricated using the powders prepared by the self-propagating high-temperature synthesis (SHS). The electrical conductivity was evaluated from an a.c. impedance measurements. The conductivity of SrZr$_{0.92}$Yb$_{0.08}$O$_{3-\delta}$ was 1.8$\times$10$^{-3}$ Scm$^{-1}$ at $900^{\circ}C$ in dry air atmosphere and its activation energy was 0.50 eV. The conductivity in wet air was larger, compared with the dry air, and the activaton energy of SrZr$_{0.92}$Yb$_{0.08}$O$_{3-\delta}$ in wet air was 0.40 eV.

• Journal of Hydrogen and New Energy
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• v.35 no.1
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• pp.48-55
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• 2024

The electrochemically active site of mixed ionic and electronic conductor (MIEC) as a cathode material is restricted to the triple phase boundary in protonic ceramic fuel cells (PCFCs) due to the insufficient of proton-conducting properties of MIEC. This study primarily focused on expanding the electrochemically active site by La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ(LSCF6428)-BaZr_0.4Ce_0.4Y_0.1Yb_0.1O_3-δ (BZCYYb4411) composite cathode. The electrochemical properties of the composite cathode were evaluated using anode-supported PCFC single cells. In comparison to the LSCF6428 cathode, the peak power density of the LSCF6428-BZCYYb4411 composite cathode is much enhanced by the reduction in both ohmic and non-ohmic resistance, possibly due to the increased electrochemically active site.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.695-699
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• 2009

We studied the transfer of oxygen vacancy and proton in Y-doped BaZr$O_3$ (BYZ) using density functional theory (DFT). An oxygen vacancy was generated in the $2{\times}2{\times}2$ BYZ superstructure by replacing two Zr atoms with two Y atoms to satisfy the charge neutrality condition. The O vacancy transfer between the first and second nearest O atom sites from a Y atom showed the lowest activation energy barrier of 0.42 eV, compared to the other transfers between first and first, and second and second in the superstructure. Two protons were inserted in the structure by adding a proton and hydroxyl that were supplied by the dissociation of a water molecule. The two protons bonded to the first and second nearest O atoms were energetically the most favorable. The activation energy barrier for a proton transfer in the structure was 0.51 eV, when either proton transferred to its neighbor O atom. This value was well matched with the experimentally determined one.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.785-786
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• 2012

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.213-218
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• 2005

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.415-422
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• 2003

BaZr $O_3$-based proton conductors in which B-site cations are partially substituted by Ce and Yb were fabricated by a solid state reaction method. The electrical properties of the specimens were measured by using impedance analyzer in dry air and wet air atmospheres. The electrical conductivity showed higher value in wet air than in dry air at below $600^{\circ}C$. As the Ce content increased, the electrical conductivity increased. Among four compositions, BaZ $r_{0.8}$C $e_{0.15}$Y $b_{0.05}$ $O_3$$_{-{\delta}}$ specimen showed the highest electrical conductivity,1.72$\times$10$^{-3}$ S$cm^{-1}$ /, at 80$0^{\circ}C$. In the low temperature region, the electrical conductivity was higher in wet air than in dry air. However, as the temperature increased, the proton conductivity reduced and thus the electrical conductivity showed similar value at approximately $700^{\circ}C$.

• Journal of Hydrogen and New Energy
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• v.22 no.5
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• pp.569-578
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• 2011

The $SiO_2$ membranes for polymer electrolyte membrane fuel cell (PEMFC) are preapared by electrospinning method. It leads to high porosity and surface area of membrane to accommodate the proton conducting materials. The composite membrane was prepared by impregnating of Nafion ionomer into the pores of electrospun $SiO_2$ membranes. The $SiO_2$:heteropolyacid (HPA) nano-particles as a inorganic proton conductor were prepared by microemulsion process and the particles are added to the Nafion ionomer. The characterization of the membranes was confirmed by field emission scanning electron microscope (FE-SEM), thermogravimetry analysis (TGA), and single cell performance test for PEMFC. The Nafion impregnated electrospun $SiO_2$ membrane showed good thermal stability, satisfactory mechanical properties and high proton conductivity. The addition of the $SiO_2$:HPA nano-particle improved proton conductivity of the composite membrane, which allow further extension for operation temperature in low humidity environments. The composite membrane exhibited a promising properties for the application in high temperature PEMFC.

• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.213-221
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• 1998

$BaCe_{0.9}Gd_{0.1_O_{2.95}$ powder was synthesized by oxalate coprecipitation method. Precipitate with a stoichimetric ratio of the cations was prepared by adding a mixture of Ba, Ce and Gd nitrate solution to an oxalic acid solution at pH 4. Reaction between the constituent oxides to form a perovskite phase was initiated at $800^{\circ}C$ and a single phase $BaCe_{0.9}Gd_{0.1_O_{2.95}$ powder having good sinterability was obtained after calcination at $1000^{\circ}C$. Sintering green compacts of this powder for 6 h showed a considerable densification to start at $1100^{\circ}C$ and resulted in 93% and 97% relative densities at $1300^{\circ}$ and at $1450^{\circ}C$, respectively. Whereas the power compacts prepared by solid state reaction had lower relative densities, 78% at $1300^{\circ}$and 90% at $1450^{\circ}C$. Fine particles of $CeO_2$ second phase were observed in the surface of the sintered compacts. This was attributed to the evaporation of BaO from the surface that had been exposed during thermal etching.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.679-684
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• 1999

Specimens of SrZr0.95Ga0.05O3-$\delta$, SrZr0.95Y0.05O3-$\delta$, BaZr0.95Ga0.05O3-$\delta$ and BaZr0.95Y0.05O3-$\delta$ were fabricated by a solid-state reaction method and subsequent sintering at 150$0^{\circ}C$ to 1$600^{\circ}C$ The microstructures and electrical characteristics of the specimens were studied. Only BaZr0.95Ga0.05O3-$\delta$ showed dense microstructure and had typical impedance spectra at various temperature. Its electrical conductivity by impedance analysis was 2.7$\times$10-3$\Omega$-1.cm-1 at 90$0^{\circ}C$ in air. The BaZr0.95Ga0.05O3-$\delta$ exhibited lower grain rsistance in wet atmosphere than in dry atmosphere and the reduction of resistance is due to the proton conduction.