Properties and performance of BaxSr1−xCo0.8Fe0.2O3−δ materials for oxygen transport membranes

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Vente, Jaap F. and McIntosh, Steven and Haije, Wim G. and Bouwmeester, Henny J.M. (2006) Properties and performance of BaxSr1−xCo0.8Fe0.2O3−δ materials for oxygen transport membranes. Journal of Solid State Electrochemistry, 10 (8). pp. 581-588. ISSN 1432-8488

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Abstract:The present paper discusses the oxygen transport properties, oxygen stoichiometry, phase stability, and chemical and mechanical stability of the perovskites $${\text{Ba}}_{{0.5}} {\text{Sr}}_{{0.5}} {\text{Co}}_{{0.8}} {\text{Fe}}_{{0.2}} {\text{O}}_{{3 - \delta }} $$ (BSCF) and $${\text{SrCo}}_{{0.8}} {\text{Fe}}_{{0.2}} {\text{O}}_{{3 - \delta }} $$(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-thick membranes, BSCF is preferred as a membrane material due to its phase stability. However, BSCF’s long-term stable performance remains to be confirmed. The deviation from ideal oxygen stoichiometry for both materials is high: δ>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.
Item Type:Article
Copyright:© 2006 Springer
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Science and Technology (TNW)
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Link to this item:http://purl.utwente.nl/publications/71889
Official URL:http://dx.doi.org/10.1007/s10008-006-0130-2
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