Effect of composition of (La0.8Sr0.2MnO3–Y2O3-stabilized ZrO2) cathodes: Correlating three-dimensional microstructure and polarization resistance

Autor: Sherri Rukes, J. Scott Cronin, Daniel R. Mumm, Hsun-Yi Chen, James R. Wilson, Katsuyo Thornton, Scott A. Barnett, Anh T. Duong
Rok vydání: 2010
Předmět:
Zdroj: Journal of Power Sources. 195:1829-1840
ISSN: 0378-7753
DOI: 10.1016/j.jpowsour.2009.09.074
Popis: Composite La0.8Sr0.2MnO3 (LSM)–Y2O3-stabilized ZrO2 (YSZ) cathodes with compositions ranging from 30:70 to 70:30 wt.% LSM:YSZ were studied both electrochemically and microstructurally. Polarization resistance was lowest for the 50 wt.% YSZ composition, and increased symmetrically as the composition deviated from this value. Serial-sectioning using focused ion beam-scanning electron microscopy was implemented to reconstruct the three-dimensional cathode microstructure. Various averaged structural parameters were determined versus composition, including phase volume fractions, surface area densities, total triple-phase boundary (TPB) densities, interfacial curvatures, phase tortuosities, and the levels of phase connectivity. Typically >90% of the pore and YSZ networks were found to be intra-connected to the surrounding phase, but the LSM networks showed lower connected fractions, as low as 37.5% for a LSM weight fraction of 30%. The composition dependences of the total TPB density and electrochemically-active TPB density (i.e., TPB's on three fully intra-connected phases) were shown to agree reasonably well with simple “sphere-packing” structural models. An electrochemical model that accounted for the linear-specific resistance of TPB's, phase intra-connectivity, and oxygen ion transport in the YSZ as influenced by its tortuosity, was found to provide reasonable agreement with the measured polarization resistance versus composition.
Databáze: OpenAIRE
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