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Title:
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Properties and performance of BaxSr1-xCo0.8Fe0.2O3-d materials for oxygen transport membranes
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Author(s):
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Published by:
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Publication date:
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ECN
Energy Efficiency in Industry
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1-5-2006
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ECN report number:
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Document type:
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ECN-RX--06-081
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Article (scientific)
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Number of pages:
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8
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Published in: Journal of Solid State Electrochemistry (DOI 10.1007/s10008-006-0130-2). (Springer), , , Vol., p.-.
Abstract:
The present paper discusses the oxygen transport properties, oxygen stoichiometry, phase stability, and chemical and mechanical stability of the perovskites Ba0:5Sr0:5Co0:8Fe0:2O3d (BSCF) and SrCo0:8Fe0:2O3d (SCF) for air separation applications. The low oxygen conductive brownmillerite phase in SCF is characterized using in-situ neutron diffraction, thermographic analysis and temperature programmed desorption but this phase is not present for BSCF under the conditions studied. Although both materials show oxygen fluxes well above 10 ml/cm2·min at T=1,273 K and pO2=1 bar for self-supporting, 200 µm-thickmembranes, BSCF is preferred as amembrane material due to its phase stability. However, BSCF’s longterm
stable performance remains to be confirmed. The deviation fromideal oxygen stoichiometry for bothmaterials is high: d>0.6. The thermal expansion coefficients of BSCF and SCF are 24×10-6 and 30×10-6 K-1, respectively, as
determined from neutron diffraction data. The phenomenon of kinetic demixing has been observed at pO2<10-5 bar, resulting in roughening of the surface and enrichment with alkaline earth metals. Stress–strain curves were determined and indicated creep behavior that induces undesired ductility at T=1,073 K for SCF. Remedies for mechanical and chemical instabilities are discussed.
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