• Journal of the Korean Ceramic Society
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• v.44 no.12
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• pp.727-732
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• 2007

In order to fabricate a highly performing cathode for low-temperature type solid oxide fuel cells working at below $700^{\circ}C$, electrode microstructure control and electrode polarization measurement were performed with an electronic conductor, $La_{0.8}Sr_{0.2}MnO_3$ (LSM) and a mixed conductor, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$(LSCF). For both cathode materials, when $Sm_{0.2}Ce_{0.8}O_2$ (SDC) buffer layer was formed between the cathode and yttria-stabilized zirconia (YSZ) electrolyte, interfacial reaction products were effectively prevented at the high temperature of cathode sintering and the electrode polarization was also reduced. Moreover, cathode polarization was greatly reduced by applying the SDC sol-gel coating on the cathode pore surface, which can increase triple phase boundary from the electrolyte interface to the electrode surface. For the LSCF cathode with the SDC buffer layer and modified by the SDC sol-gel coating on the cathode pore surface, the cathode resistance was as low as 0.11 ${\Omega}{\cdot}cm^2$ measured at $700^{\circ}C$ in air atmosphere.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.46-48
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• 2004

A micro-scale discharge device has been fabricated using MEMS technology and failure mechanisms during DC discharge are investigated for the microstructure. The failure of sustaining the plasma is mainly caused by either open or short of the micro-electrodes, both resulting from the sputtered metal atoms during the DC discharge. The glow discharge lifetime of the microstructures is found to depend on bias circuit scheme as well as the electrode structure. Based on the understanding of the failure mechanism, a novel microstructure is suggested to improve discharge lifetime and the longer lifetime is experimentally demonstrated. In addition to the failure mechanism, an electric breakdown between two electrodes with microns gap are studied using micromachined metal structures. The electrode gap is able to be accurately controlled by thickness of a sacrificial layer and the electric breakdown was measured while varying the gap from $2{\mu}m$ to $20{\mu}m$. The electric breakdown behavior was found to highly depend on the electrode material, which was not considered in Paschen's law.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.86-91
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• 2010

Among various fuel cells, solid oxide fuel cells (SOFCs) offer the highest energy efficiency, when taking into account the thermal recycling of waste heat at high temperature. However, the highest efficiency and lowest pollution for a SOFC can be achieved through the sophisticated control of its constituent components such as electrodes, electrolytes, interconnects and sealing materials. The electrochemical conversion efficiency of a SOFC is particularly dependent upon the performance of its electrode materials. The electrode materials should meet highly stringent requirements to optimize cell performance. In particular, both mass and charge transport should easily occur simultaneously through the electrode structure. Matter transport or charge transport is critically related to the configuration and spatial disposition of the three constituent phases of a composite electrode, which are the ionic conducting phase, electronic conducting phase, and the pores. The current work places special emphasis on the quantification of this complex microstructure of composite electrodes. Digitized images are exploited in order to obtain the quantitative microstructural information, i.e., the size distributions and interconnectivities of each constituent component. This work reports regarding zirconia-based composite electrodes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.4
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• pp.418-421
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• 2023

Multilayer Ceramic Capacitors (MLCCs) are essential passive components in the electronics industry, known for their high capacitance due to the multilayer structure comprising inner electrodes and dielectric layers. Nickel electrodes are commonly used in MLCCs as the inner electrodes, and to prevent oxidation during the co-firing of the dielectric layers with nickel electrodes, reducing atmosphere is required. However, reducing atmosphere sintering can also induce a reduction of the dielectric, necessitating precise control of oxygen partial pressure. To explore the possibility of using oxide electrodes that do not require reducing atmosphere sintering, we analyze the electrical properties of nickel oxide (NiO) as a potential candidate. As a preliminary study on its use as an alternative inner electrode, the correlation between microstructure and electrical properties of bulk NiO under different sintering conditions was investigated to gain insights into the conduction mechanisms of the material.

• Journal of the Korean Ceramic Society
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• v.41 no.3
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• pp.229-234
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• 2004

In this study, we proposed new forming process for a porous ceramic body with unique pore structure. h tubular-type porous NiO-YSZ body with radially aligned pore channels was prepared by freeze-drying of aqueous slurry. A NiO-YSZ slurry was poured into the mold, which was designed to control the crystallization direction of the ice, followed by freezing. Thereafter the ice was sublimated at a reduced pressure. SEM observations revealed that the NiO-YSZ porous body showed aligned large pore channels parallel to the ice growth direction, and fine pores are formed around the outer surface of the tube. It was considered that the difference in the ice growth rate during the freezing process resulted in such a characteristic microstructure. Bilayer consisting of dense thin electrolyte film of YSZ onto the tubular type porous body has been successfully fabricated using a slurry-coating process followed by co-firing. It was regarded that the obtained bilayer structure is suitable for constructing electrode-support type electrochemical devices such as solid oxide fuel cells.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.308-308
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• 2012

Electrodeposition of thermoelectric materials, including binary and ternary compounds, have been attracting attentions, because its many advantages including cost-effectiveness, rapid deposition rate, and ease of control their microstructure and crystallinity by adjusting electrodeposition parameters. In this work, $Bi_xTe_y$ films were potentiostatically electrodeposited using Au/Ni(80/20 nm)/Si substrate as the working electrode in solutions consisting of 10mM $TeO_2$ and 1M $HNO_3$ where $Bi(NO_3)_3$ was varied from 2.5 to 10 mM. Prior to electrodeposition potentiostatically, linear sweep voltammograms (LSV) were acquired with a standard three-electrode cell. The $Bi_xTe_y$ films deposited using the electrolyte containing low Bi ions shows p-type conductivity, which might be attributed by the large incorporation of Te phases. Near stoichiometric $Bi_2Te_3$ thin films were obtained from electrolytes containing 5mM $Bi(NO_3)_3$. This film shows the maximum Seebeck coefficient of $-100.3{\pm}12.7{\mu}V/K$. As the increase of Bi ions in electrolytes decreases the Seebeck coefficient and resistivity. The maximum power factor of $336.2{\mu}W/m{\cdot}K^2$ was obtained from the film deposited using the solution of 7.5mM $Bi(NO_3)_3$.