abstract
The thermal and chemical expansion of Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) and SrCo0.8Fe0.2O3-delta (SCF) mixed ionic-electronic conductors were studied in combination with oxygen nonstoichiometry (delta) at 298-1223 K and p(O-2) = 10(-4) to 1.00 atm. In order to minimize the effects of phase separation or oxygen-vacancy ordering processes, the data were collected in dynamic cooling mode using dense ceramic samples. The procedure was justified by a very fast equilibration at given p(O-2) in high-temperature range demonstrated for ceramics samples with different specific surface area. The difference in nonstoichiometry of BSCF and SCF at temperatures >= 973 K was found to be <= 0.03 oxygen atoms per formula unit. BSCF demonstrates favorably smaller chemical expansion compared to SCF and many other mixed conductors, originating from smaller delta variations and larger unit cell less sensitive to temperature and nonstoichiometry changes. Excessive thermochemical expansion impedes however the use of BSCF in single-phase fuel cell cathodes and planar mixed-conducting membranes. (C) 2013 Elsevier Ltd. All rights reserved.
keywords
PEROVSKITE-TYPE OXIDES; SITU NEUTRON-DIFFRACTION; CHEMICAL EXPANSION; OXYGEN PERMEABILITY; FUEL-CELLS; PHASE-STABILITY; BA0.5SR0.5CO0.8FE0.2O3-DELTA PEROVSKITE; INTERMEDIATE TEMPERATURES; ELECTRICAL-PROPERTIES; EXCHANGE KINETICS
subject category
Materials Science
authors
Yaremchenko, AA; Mikhalev, SM; Kravchenko, ES; Frade, JR
our authors
Aleksey Yaremchenko
Principal Researcher
Jorge Ribeiro Frade
Retired Professor
Sergey Mikhalev
Post-Doc FellowshipProjects
ORIEL - Oriented Lanthanum Silicate Thin Film Electrolytes for IT-SOFCS (PTDC/CTM-CER/118933/2010)
acknowledgements
This work was supported by the FCT, Portugal (projects PTDC/CTM-CER/118933/2010, PTDC/CTM-CER/114561/2009 and PEst-C/CTM/LA0011/2013, and Ciencia program).