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Research Papers

Nanoscale Gd-Doped CeO2 Buffer Layer for a High Performance Solid Oxide Fuel Cell

[+] Author and Article Information
Cornelia Endler-Schuck

Institut für Werkstoffe der Elektrotechnik (IWE), Karlsruher Institut für Technologie (KIT), Adenauerring 20b, DE-76131 Karlsruhe, Germanycornelia.endler@kit.edu

André Weber

Institut für Werkstoffe der Elektrotechnik (IWE), Karlsruher Institut für Technologie (KIT), Adenauerring 20b, DE-76131 Karlsruhe, Germany

Ellen Ivers-Tiffée

Institut für Werkstoffe der Elektrotechnik (IWE) and DFG Center for Functional Nanostructures (CFN), Karlsruher Institut für Technologie (KIT), Adenauerring 20b, DE-76131 Karlsruhe, Germany

Uwe Guntow

 Fraunhofer Institute for Silicate Research (ISC), Neunerplatz 2, DE-97082 Würzburg, Germany

Johannes Ernst, Jürgen Ruska

 CeramTec AG, Lorenzreuther Straße 2, DE-95615 Marktredwitz, Germany

J. Fuel Cell Sci. Technol 8(4), 041001 (Mar 25, 2011) (5 pages) doi:10.1115/1.4003016 History: Received February 11, 2010; Revised July 27, 2010; Published March 25, 2011; Online March 25, 2011

Gd2O3-doped ceria (GCO) is irreplaceable as interface/buffer layer between a mixed conducting cathode such as La0.58Sr0.4Co0.2Fe0.8O3-δ (LSCF) and an 8mol%Y2O3 stabilized ZrO2 (8YSZ) thin film electrolyte. To meet the demands of high performance, indispensable characteristics of this interface (LSCF/GCO/8YSZ) are (i) no reaction of GCO with LSCF or YSZ and (ii) a GCO layer that is defect-free (closed porosity, no cracks). It is well known that state-of-the-art screen printed and sintered GCO buffer layers are imperfect and ultimately reduce the overall performance. This study concentrates on the evaluation of nanoscaled GCO thin films integrated into anode supported cells (ASC). GCO thin films were deposited on 8YSZ electrolyte by a low temperature metal organic deposition (MOD) process. MOD is preferable because it is a versatile technique for large scale and low cost fabrication for various material compositions. The authors investigated the influence of preparation parameters with respect to chemical homogeneity and film quality (pores, cracks) of GCO thin films with a constant film thickness between 50 nm and 100 nm. Electrochemical performance of anode supported cells employing MOD derived GCO thin films will be presented in terms of ohmic resistance (ASRΩ) and will be evaluated in contrast to screen printed and sintered GCO thick films. Nanoscale MOD derived thin films with low processing temperatures and dense film qualities were vastly superior to state-of-the-art GCO and beneficial to the overall cell performance.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Thermogravimetry and DSC analyses of GCO coating sol

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Figure 2

Cross section of GCO layers differing in thickness

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Figure 3

Crack free and homogeneous GCO layer on 8YSZ substrate

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Figure 4

ASRΩ for a MOD GCO layer on top of an 8YSZ thin film electrolyte

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Figure 5

ASRΩ for a screen printed and sintered GCO layer on top of an 8YSZ thin film electrolyte

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Figure 6

Calculated ASRΩ of the layers 8YSZ electrolyte, 8YSZ/GCO interdiffusion zone, and screen printed GCO layer versus temperature

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Figure 7

Electrochemical impedance spectra of the four different cells with MOD GCO interlayer (A–C) and screen printed GCO interlayer (D) for T=600°C

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Figure 8

ASRΩ versus temperature of different cells compared with the calculated ASRΩ. “SP” means “screen printed.” The LSCF cathode of cell D is sintered at T=1080°C.

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Figure 9

Arrhenius plots of Sr-zirconate materials manufactured by the Pechini method (14). Formulae refer to the gross chemical composition. The literature values are compared with conductivities of unknown layer found in this study (●), which increases the ohmic resistance.

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