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Research Papers

Effect of Processing Conditions on Curvature of Anode/Electrolyte SOFC Half-Cells Fabricated by Electrophoretic Deposition

[+] Author and Article Information
Michael K. Lankin, Kunal Karan

Department of Chemical Engineering, Queen’s University, Kingston ON, K7L 3N6, Canada; Queen’s-RMC Fuel Cell Research Centre, Kingston ON, K7L 5L9, Canada

J. Fuel Cell Sci. Technol 6(2), 021001 (Feb 20, 2009) (8 pages) doi:10.1115/1.2971044 History: Received February 02, 2007; Revised July 16, 2007; Published February 20, 2009

Thin-electrolyte anode-supported solid oxide fuel cells (YSZ/NiO–YSZ) were fabricated for intermediate-temperature operation using electrophoretic deposition (EPD). During cosintering, the half-cells were observed to warp—an undesirable characteristic—due to mismatch in the sintering rates. The influence of the temperature for anode presintering—a key processing step—on the curvature of the half-cells induced by sintering was investigated over 7001400°C. It was found that the maximum curvature occurred for an anode presintered at 900°C, while the minimum was observed at 1200°C. Anode presintering temperature was also found to affect the rate of electrophoretic deposition. At low presintering temperatures, the rate of EPD increased due to the enhancement in substrate (anode) electronic conductivity as a result of an increased percolating network of NiO. Further increases in presintering temperature, however, resulted in a decrease in the EPD rate due to the formation of a surface layer with poor electronic conductivity as a result of NiO diffusion from the NiO-YSZ anode to the sintering crucible.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the curvature induced in a bilaminate due to sintering stress mismatch

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Figure 2

Backscattered SEM micrographs depicting the variation of the sintered YSZ thickness at various presinter temperatures for a constant deposition time (tdep=180s). (a) TPS=700°C, (b) TPS=900°C, (c) TPS=1200°C.

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Figure 3

Average SEM-observed thickness of sintered YSZ electrolyte (tdep=180s) on NiO-YSZ anode as a function of presintering temperature

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Figure 4

Electrical conductivity of NiO-YSZ anodes at 250°C in air, as a function of anode presintering temperature

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Figure 5

Backscattered SEM micrographs depicting the concentrations of NiO and YSZ on the surface of NiO-YSZ anodes as a function of the presintering temperature. The light and dark regions represent YSZ and NiO, respectively. (a) 900°C, (b) 1400°C.

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Figure 6

Energy-dispersive X-ray spectrum for NiO-YSZ anodes as a function of presinter temperature. (a) 700°C, surface scan; (b) 1400°C, surface scan.

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Figure 7

Plot of ratio of zirconia and nickel EDS peak heights for the surface of NiO-YSZ anodes as a function of anode presintering temperature

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Figure 8

Effect of competing mechanisms on the electrolyte layer thickness as a function of anode presintering temperature

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Figure 9

Schematic diagram depicting the effect of presintering temperature on the microstructure of a NiO/YSZ anode. High presintering temperatures lead to a nickel-deficient region. The light and dark regions represent YSZ and NiO, respectively.

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Figure 10

Curvature induced in anode/electrolyte half-cell due to sintering stress mismatch. (TPS=1000°C; tdep=180s. Sintering: 5h at 500°C, 5h at 1400°C, β=2°C∕min.)

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Figure 11

Absolute and thickness-normalized curvature as a function of anode presintering temperature. (tdep=180s. Sintering: 5h at 500°C, 5h at 1400°C; β=2°C∕min.)

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Figure 12

Absolute curvature of sintered EPD YSZ/NiO-YSZ half-cells as a function of presinter temperature for a sintering dwell-time of 2h

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Figure 13

Absolute curvature of sintered EPD (tdep=180s) YSZ/NiO-YSZ half-cells as a function of sintering dwell-time

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