• 한국세라믹학회지
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• 제43권5호
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• pp.299-303
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• 2006

In this paper, anode supported SOFC with columnar structured YSZ electrolyte was fabricated via Electron Beam Physical Vapor Deposition (EBPVD) method. Liquid condensation process was employed for the preparation of NiO-YSZ substrate and the high power electron beam deposition method was used for the deposition of YSZ electrolyte film. Double layered cathode with LSM-YSZ and LSM was printed on electrolyte via screen-printing method and fired at $1150^{\circ}C$ in air atmosphere for 3 h. The electrochemical performance and the long-term stability of $5{\times}5cm^2$ single cell were investigated with DC current-voltage characteristics and AC-impedance spectroscopy. According to the investigation, $5{\times}5cm^2$ sized unit cell showed the maximum power density of around $0.76W/cm^2$ at $800^{\circ}C$ and maintained the stable performance over 400 h.

• Korean Chemical Engineering Research
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• 제50권3호
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• pp.562-566
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• 2012

본 논문에서는 세그먼트 관형 고체산화물 연료전지(SOFC)의 설계 및 제작과 특성 분석을 다루고 있다. 관형 세라믹 지지체는 압출 공정을 통하여 제작하였으며, NiO-YSZ 연료극과 YSZ 전해질은 담금 코팅법을 통해 세라믹 지지체에 코팅하였다. 코팅된 세라믹 지지체를 $1,350^{\circ}C$에서 5시간 동안 열처리하였으며, $10{\mu}m$ 미만의 치밀하고, 균열이 없는 YSZ 전해질 층을 얻을 수 있었다. 또한 열처리된 세라믹 지지체에 LSM-YSZ/LSM/LSCF로 구성된 다층 구조 공기극을 담금법으로 코팅하여 $1,150^{\circ}C$에서 열처리하였다. 세라믹 관형 지지체에 코팅된 세그먼트 SOFC 셀은 Ag-glass 연결재를 사용하여 전기적으로 직렬 연결하였으며, 수소연료 유량과 운전 온도에 따른 세그먼트 SOFC의 성능 변화를 측정하였다.

• 한국세라믹학회지
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• 제49권5호
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• pp.404-411
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• 2012

The reliability of solid oxide fuel cells (SOFCs) particularly depends on the high quality of solid oxide electrolytes. The application of thinner electrolytes and multi electrolyte layers requires a more reliable characterization method. Most of the investigations on thin film solid electrolytes have been made for the parallel transport along the interface, which is not however directly related to the fuel cell performance of those electrolytes. In this work an array of ion-blocking metallic Ti/Au microelectrodes with about a $160{\mu}m$ diameter was applied on top of an ultrathin ($1{\mu}m$) yttria-stabilized-zirconia/gadolinium-doped-ceria (YSZ/GDC) heterolayer solid electrolyte in a micro-SOFC prepared by PLD as well as an 8-${\mu}m$ thick YSZ layer by screen printing, to study the transport characteristics in the perpendicular direction relevant for fuel cell operation. While the capacitance variation in the electrode area supported the working principle of the measurement technique, other local variations could be related to the quality of the electrolyte layers and deposited electrode points. While the small electrode size and low temperature measurements increaseed the electrolyte resistances enough for the reliable estimation, the impedance spectra appeared to consist of only a large electrode polarization. Modulus representation distinguished two high frequency responses with resistance magnitude differing by orders of magnitude, which can be ascribed to the gadolinium-doped ceria buffer electrolyte layer with a 200 nm thickness and yttria-stabilized zirconia layer of about $1{\mu}m$. The major impedance response was attributed to the resistance due to electron hole conduction in GDC due to the ion-blocking top electrodes with activation energy of 0.7 eV. The respective conductivity values were obtained by model analysis using empirical Havriliak-Negami elements and by temperature adjustments with respect to the conductivity of the YSZ layers.

• 한국세라믹학회지
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• 제48권5호
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• pp.479-484
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• 2011

In this paper, investigations of thick film $La_{0.75}Sr_{0.25}Ga_{0.8}Mg_{0.16}Fe_{0.04}O_{3-{\delta}}$ (LSGMF) cells fabricated via spin coating on either NiO-YSZ anode or $La_{0.7}Sr_{0.3}Ga_{0.6}Fe_{0.4}O_3$ (LSGF) cathode substrates are presented. A La-doped $CeO_2$ (LDC) layer is inserted between NiO-YSZ and LSGMF in order to prevent reactions from occurring during co-firing. For the LSGF cathode-supported cell, no interlayer was required because the components of the cathode are the same as those of LSGMF with the exception of Mg. An LSGMF electrolyte slurry was deposited homogeneously on the porous supports via spin coating. The current-voltage characteristics of the anode and cathode supported LSGMF cells at temperatures between $700^{\circ}C$ and $850^{\circ}C$ are described. The LSGF cathode supported cell demonstrates a theoretical OCV and a power density of ~420 mW $cm^2$ at $800^{\circ}C$, whereas the NiO-YSZ anode supported cell with the LDC interlayer demonstrates a maximum power density of ~350 mW $cm^2$ at $800^{\circ}C$, which decreased more rapidly than the cathode supported cell despite the presence of the LDC interlayer. Potential causes of the degradation at temperatures over $700^{\circ}C$ are also discussed.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.390-397
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• 2022

The use of microwaves as the energy source for synthesis and sintering of ceramics offers substantial advantages compared to conventional gas-fired and electric resistance furnaces. Benefits include much shorter processing times and reaching the sintering temperature more quickly, resulting in superior final product quality. Most oxide ceramics poorly interact with microwave irradiation at low temperatures; thus, a more complex setup including a susceptor is needed, which makes the whole process very complicated. This investigation pursued a new approach, which enabled us to use microwave irradiation directly in poorly coupled oxides. In many solid-state electrochemical devices, the support is either metal or can be reduced to metal. Metal powders in the support can act as an internal susceptor and heat the entire cell. Then sufficient interaction of microwave irradiation and ceramic material can occur as the sample temperature increases. This microwave heating and exothermic reaction of oxidation of the support can sinter the ceramic very efficiently without any external susceptor. In this study, yttria stabilized zirconia (YSZ) and a Ni-YSZ cermet support were used as an example. The cermet was used as the support, and a YSZ electrolyte was coated and sintered directly using microwave irradiation without the use of any susceptor. The results were compared to a similar cell prepared using a conventional electric furnace. The leakage test and full cell power measurement results revealed a fully leak-free electrolyte. Scanning electron microscopy and density measurements show that microwave sintered samples have lower open porosity in the electrode support than conventional heat treatment. This technique offers an efficient way to directly use microwave irradiation to sinter thin film ceramics without a susceptor.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.214-214
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• 2010

The 0.65Pb($Mg_{1/3}Nb_{2/3})O_3-0.35PbTiO_3$ (PMN-PT) thin films with $La_{0.5}Sr_{0.5}CoO_{3-\delta}$ (LSCO) bottom electrodes were grown on $CeO_2$/YSZ/Si(001), Pt/$TiO_2$/Si and $SrTiO_3$ (STO) substrates using conventional pulsed laser deposition (PLD) at a substrate temperature of $550^{\circ}C$. Since generally the crystallographic orientation of the bottom electrode induces the orientation of the films deposited on it, it allows us to observe the influence of the PMN-PT film orientation on the electrical properties. Phi scan done on PMN-PT/LSCO thin films shows epitaxial behavior of the films grown on sto substrates and $CeO_2$/YSZ buffered Si(001) substrates, and (110) texture on Pt/$TiO_2$/Si substrates. Polarization-electricfield (P-E) measurement shows good hysteresis behavior of PMN-PT films with remnant polarization of 18.2, 8.8, and $4.4{\mu}C/cm^2$ on $CeO_2$/YSZ/Si, Pt/TiO2/Si and STO substrates respectively.

• 한국세라믹학회지
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• 제52권5호
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• pp.338-343
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• 2015

To prevent an interfacial reaction between the anode and the electrolyte layer during the conventional high-temperature co-firing process, an anode-supported type cell with a thin-film electrolyte was fabricated by low-temperature ceramic thick film coating process. Ni-GDC cermet composite was used as the anode material and YSZ was used as the electrolyte material. Open circuit voltage and maximum power density were found to strongly depend on the surface uniformity of the anode functional layer. By optimizing the microstructure of the anode functional layer, the open circuit voltage and maximum powder density of the cell increased to 1.11 V and $1.35W/cm^2$, respectively, at $750^{\circ}C$. When a GDC barrier layer was applied between the YSZ electrolyte and the LSCF cathode, the cell showed good stability, with almost no degradation up to 100 h. Anode-supported type SOFCs with high performance and good stability were fabricated using a coating process.

• 전기화학회지
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• 제4권2호
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• pp.58-64
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• 2001

기체/전해질/LSM $(La_{0.85}Sr_{0.15}MnO_3)$ 공기극이 만나는 삼상계면 (triple phase boundary) 주위에 YSZ ($8mol\%$ yttria stabilized zirconia) 코팅막 (coating film) 을 형성하여 추가로 삼상계면을 크게 늘린 새로운 전극 미세구조를 갖는 복합 공기극 (composite cathode) 을 개발하였다. 이 복합 공기극을 전해질 두께가 약 $30{\mu}m$인 연료극 (anode)v 지지체 위에 형성하여 $700\~800{\circ}C$의 온도에서 전류전압 특성 및 교류 임피던스 분석을 실시하였다. $800^{\circ}$, 공기 및 수소 조건에서 교류 임피던스 분석 결과 1000Hz주파수 영역을 대변하는 저항성분 R1은 연료극 분극 저항에 해당하였고 100Hz주파수 영역의 저항성분 R2는 공기극 분극 저항 성분, 그리고 10Hz이하 영역의 저항성분 R3는 전극을 통한 기체확산 저항성분으로 특히, 작동 조건인 공기 및 수소 분위기에서는 연료극 쪽 반응기체에 의한 기체확산 저항 성분임을 알 수 있었다. 전지성능 측정 결과 이 복합 공기극을 장착한 전지는 $800^{\circ}C$, 공기 및 산소 조건에서 각각 $0.55W/cm^2$ $1W/cm^2$의 높은 전지성능을 나타내었다. 전류전압 곡선은 기울기가 다른 두 구간으로 구분되었으며, 낮은 전류밀도 하에서 보이는 급격한 전압감소 구간은 공기극 분극저항이 주된 성능 저하의 원인인 반면, 높은 전류밀도 하에서 나타나는 완만한 전압 감소 구간은 전해질에 관련된 분극저항이 주된 성능 저하의 원인이었다.

• 한국세라믹학회지
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• 제47권1호
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• pp.75-81
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• 2010

The feasibility of using the thin film technology in utilizing lanthanum strontium manganite (LSM) for a solid oxide fuel cell (SOFC) cathode in a low-temperature regime is investigated in this study. Thin film LSM cathodes were fabricated using pulsed laser deposition (PLD) on anode-supported SOFCs with yttria-stabilized zirconia (YSZ) electrolytes. Although cells with a 1 ${\mu}m$-thick LSM cathode showed poor low-temperature cell performance compared to that of a cell with a bulk-processed cathode due to the lack of a triple-phase boundary length, the cell with 200 nm-thick gadolinia-doped ceria (GDC) inserted between the LSM and YSZ showed enhanced performance and more stable operation characteristics in a comparison of a cell without a GDC layer. We postulate that the GDC layer likely improved the cathode adhesion, therefore contributing to the improvement of the cell performance instead of serving as an interfacial reaction buffer.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.358-359
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• 2006

Ru-C nano-composite films were prepared by MOCVD, and their microstructures and their electrode properties for oxygen gas sensors were investigated. Deposited films contained Ru particles of 5-20 nm in diameter dispersed in amorphous C matrix. The AC conductivities associating to the interface charge transfer between Ru-C composite electrode and YSZ electrolyte were 100-1000 times higher than that of conventional paste-Pt electrodes. The emf values of the oxygen gas concentration cell constructed from the nano-composite electrodes and YSZ electrolyte showed the Nernstian theoretical values at low temperatures around 500 K. The response time of the concentration cell was 900 s at 500 K.