• The Korean Journal of Ceramics
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• 제7권2호
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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.

• 전기화학회지
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• 제11권1호
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• pp.22-32
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• 2008

청정에너지의 중요성이 부각됨에 따라 수소연료를 활용한 고효율, 무공해 전력 공급원인 연료전지에 대한 관심이 증가하고 있다. 연료전지는 전기화학 반응에 의한 화학에너지를 직접 전기에너지로 변환시키는 장치로 자동차, 우주항공, 산업 및 가정용 발전 등에 적용할 수 있는 잠재력이 있다. 최근 재료 및 에너지 변환공정 차원에서 바람직한 $200{\sim}500^{\circ}C$의 온도범위에서 작동하는 중온형 연료전지에 대한 새로운 인식과 이 온도범위에서 사용 가능한 수소이온 전도성 물질의 개발 필요성이 요구되고 있다. 본 논문은 고체 수소이온 전도체의 특성과 기술 현황을 소개하고, perovskite형 고체 무기 산화물을 이용한 중온형 연료전지 응용에 관한 연구에 대하여 고찰하였다.

• 한국세라믹학회지
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• 제48권2호
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• pp.195-199
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• 2011

The effect of copper oxide on migration and interaction of protons in barium zirconate was investigated using density functional theory. One copper atom was substituted for a zirconium atom site, and a proton was added to a $3{\times}3{\times}3$ barium zirconate superstructure. An energy barrier of 0.89 eV for proton migration was the highest among several energy barriers. To investigate the interaction between multiple protons and a copper atom, two protons were added to the superstructure. Various proton positions were determined by the interaction between the two protons and the copper atom.

• 한국세라믹학회지
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• 제47권5호
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• pp.474-478
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• 2010

We studied the energy barrier for proton conduction with volume variation in $BaZrO_3$ using a first principles study to investigate an optimum volume for the proton conduction. The volume increase of $BaZrO_3$ was expected to decrease the energy barrier for proton rotation and to increase that for proton transfer, and these trends could be extrapolated when the volume was decreased. However, the energy barriers for the proton transfer with the volume decrease were increased, while all the other energy barriers varied as expected. We could explain this unexpected behavior by the bent Zr-O-Zr structure, when the volume was decreased.

• 한국수소및신에너지학회논문집
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• 제22권5호
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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.

• 한국자기공명학회논문지
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• 제18권1호
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• pp.41-46
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• 2014

In order to obtain information on the structural geometry of $NH_4HSeO_4$ near the phase transition temperature, the spectrum and spin-lattice relaxation time in the rotating frame $T_{1{\rho}}$ for the ammonium and hydrogen-bond protons were investigated through $^1H$ MAS NMR. $T_{1{\rho}}$ for the hydrogen-bond protons abruptly decreased at high temperature and it is associated with the change in the structural geometry in $O-H{\cdots}O$ bonds. This mobility of the hydrogen-bond protons may be the main reason for the high conductivity.

• 한국세라믹학회지
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• 제51권4호
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• pp.271-277
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• 2014

To overcome the limitations of the solid oxide fuel cells (SOFCs) due to the high temperature operation, there has been increasing interest in proton conducting fuel cells (PCFCs) for reduction of the operating temperature to the intermediate temperature range. In present work, the perovskite $BaCe_{0.85-x}Zr_xY_{0.15}O_{3-\delta}$ (BCZY, x = 0.1, 0.3, 0.5, and 0.7) were synthesized via solid state reaction (SSR) and adopted as an electrolyte materials for PCFCs. Powder characteristics were examined using X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Brunauer, Emmett and Teller (BET) surface area analysis. Single phase BCZY were obtained in all compositions, and chemical stability was improved with increasing Zr content. Anode-supported cell with $Ni-BaCe_{0.55}Z_{0.3}Y_{0.15}O_{3-\delta}$ (BCZY3) anode, BCZY3 electrolyte and BCZY3-$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-\delta}$ (BSCF) composite cathode was fabricated and electrochemically characterized. Open-circuit voltage (OCV) was 1.05 V, and peak power density of 370 ($mW/cm^2$) was achieved at $650^{\circ}C$.

• The Korean Journal of Ceramics
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• 제4권3호
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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.

• 한국세라믹학회지
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• 제47권1호
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• pp.71-74
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• 2010

We have investigated protonic conduction in highly dense (>98%) polycrystalline Y-doepd $BaZrO_3$ (BYZ) ceramic with an average grain size of ~85 nm. It is observed that the protonic conductivity across the grain boundaries in this nano-crystallilne BYZ (n-BYZ) is significantly higher than the microcrystalline counterpart. Such a remarkable enhancement in grain boundary conductivity results in high overall conductivity that may allow this chemically stable protonic conductor to serve as a solid electrolyte for low-temperature solid oxide fuel cell applications.

• 한국수소및신에너지학회논문집
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• 제22권2호
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• pp.161-167
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• 2011

Proton conductors have attracted considerable attention for solid oxide fuel cell (SOFC), hydrogen pump, gas sensor, and membrane separators. Doped $SrCeO_3$ exhibits appreciable proton conductivity in hydrogen-containing atmosphere at high temperature. However commercial realization has been hampered due to the reactivity of $SrCeO_3$ with $CO_2$. The chemical stability and proton conductivity are dependent on dopant type. The purpose of this work is to investigate chemical stability of $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$ composites in $CO_2$ and $H_2$ gases. Thermogravimetric analysis (TGA) was performed in gaseous $CO_2$ and electrical conductivity of the composites were also measured between 500 and $900^{\circ}C$ in air and $H_2$ atmosphere. $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$ composite membranes showed good chemical stability of in $CO_2$ atmosphere and high conductivity at hydrogen condition. The hydrogen permeation of $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$ composite membranes was investigated as a function of volumetric content of $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}$. The $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$(6:4) membrane with a thickness of 1.0 mm showed the highest hydrogen permeability with the flux reaching of 0.12 $ml/min{\cdot}cm^2$ at $800^{\circ}C$ in 100%$H_2/N_2$ as feed gas.