Stability, oxygen permeability and chemical expansion of Sr(Fe,Al)O3-delta- and Sr(Co,Fe)O3-delta-based membranes
authors Yaremchenko, AA; Tsipis, EV; Kovalevsky, AV; Waerenborgh, JC; Kharton, VV
nationality International
journal SOLID STATE IONICS
author keywords Mixed conductor; Composite; Perovskite; Stability; Ceramic membrane; Oxygen permeation; Dilatometry; Massbauer spectroscopy
keywords THERMAL-EXPANSION; TRANSPORT-PROPERTIES; CERAMIC MEMBRANES; MOSSBAUER-SPECTROSCOPY; STRUCTURAL STABILITY; NEUTRON-DIFFRACTION; HIGH-PRESSURE; PEROVSKITES; OXIDES; CONDUCTIVITY
abstract Perovskite-type SrFe0.7Al0.3O3-delta and SrCo0.8Fe0.2O3-delta, and two related dual-phase composites with nominal compositions (SrFeO3-delta)(0.7)(SrAl2O4)(0.3) and (SrCo0.8Fe0.2O3-delta)(0.7)(SrAl2O4)(0.3). were comparatively studied employing controlled-atmosphere dilatometry, thermogravimetry. Mossbauer spectroscopy, and measurements of steady-state oxygen permeation fluxes through dense ceramic membranes. The composite materials display lower thermal and chemical expansion compared to the parent single-phase perovskites. The thermal expansion coefficients at 1023-1223 K are however still high, (20-23) x 10(-6) K-1 at atmospheric oxygen pressure and (17-18) x 10(-6) K-1 at p(O-2) = 10 Pa, thus limiting the range of possible membrane reactor configurations. Sr(Co,Fe)O3-delta-based materials exhibit extensive vacancy-ordering processes in inert atmospheres, resulting in a slow relaxation of the oxygen nonstoichiometry, chemical expansion and oxygen permeation fluxes. In comparison to Sr(Fe,Al)O3-delta, the stability of cobalt-containing ceramics in CO2 is also poor, which leads to a partial blocking of the membrane surface by decomposition products and degradation of the oxygen transport. Thermogravimetric analysis showed that the interaction with carbon dioxide occurs even at elevated temperatures, up to 1223 K. Under high oxygen chemical potential gradients such as air/(H-2-H2O), the composite membranes showed kinetically stable operation without bulk decomposition at 1073 K. The kinetic stabilization associated with surface-limited oxygen permeation was confirmed by the conversionelectron Mossbauer spectroscopy analysis of one (SrFeO3-delta)(0.7)(SrAl2O4)(0.3) membrane exposed to dry CH4 at 1173 K, where no traces of Fe2+ and metallic iron were detected in the reduced surface layer. (C) 2010 Elsevier B.V. All rights reserved.
publisher ELSEVIER SCIENCE BV
issn 0167-2738
year published 2011
volume 192
issue 1
beginning page 259
ending page 268
digital object identifier (doi) 10.1016/j.ssi.2010.04.026
web of science category Chemistry, Physical; Physics, Condensed Matter
subject category Chemistry; Physics
unique article identifier WOS:000292848800057
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