authors |
Shaula, AL; Kharton, VV; Vyshatko, NP; Tsipis, EV; Patrakeev, MV; Marques, FMB; Frade, JR |
nationality |
International |
journal |
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY |
author keywords |
perovskites; membranes; ionic conductivity; electrical conductivity; mixed conductor; (Sr.Ca)(Fe,Al)O-3 |
keywords |
DEFECT STRUCTURE; ELECTRICAL-PROPERTIES; REDUCING ATMOSPHERE; HIGH-TEMPERATURES; PEROVSKITE; STABILITY; OXIDES; CONDUCTIVITY; EXPANSION; GAS |
abstract |
The oxygen permeability of mixed-conducting Sr1-xCaxFe1-yAlyO3-delta(x = 0-1.0; y = 0.3-0.5) ceramics at 850-1000 degreesC, with an apparent activation energy of 120-206 kJ/mol, is mainly limited by the bulk ionic conduction. When the membrane thickness is 1.0 mm, the oxygen permeation fluxes under PO2 gradient of 0.21/0.021 atm vary from 3.7 x 10(-10) mols s(-1) cm(-2) to 1.5 x 10(-7) mol s(-1) cm(-2) at 950 degreesC. The maximum solubility of Al3+ cations in the perovskite lattice of SrFe(1-y)A(y)O(3-delta) is approximately 40%, whilst the brownmillerite-type solid solution formation range in Sr1-xCax Fe0.5Al0.5O3-delta system corresponds to x > 0.75. The oxygen ionic conductivity of SrFeO3-based perovskites decreases moderately on Al doping, but is 100-300 times higher than that of brownmillerites derived from CaFe0.5Al0.5O2.5+delta. Temperature-activated character and relatively low values of hole mobility in SrFe0.7Al0.3O3-delta, estimated from the total conductivity and Seebeck coefficient data, suggest a small-polaron mechanism of p-type electronic conduction under oxidising conditions. Reducing oxygen partial pressure results in increasing ionic conductivity and in the transition from dominant p- to n-type electronic transport, followed by decomposition. The low-pO(2) stability limits of Sr1-xCaxFe1-yAlyO3-delta seem essentially independent of composition, varying between that of LaFeO3-delta and the Fe/Fe1-gammaO boundary. Thermal expansion coefficients of Sr1-xCaxFe1-yAlyO3-delta ceramics in air are 9 x 10(-6) K-1 to 16 x 10(-6) K-1 at 100-650 degreesC and 12 x 10(-6) K-1 to 24 x 10(-6) K-1 at 650-950 degreesC. Doping of SrFe1-yAlyO3-delta with aluminum decreases thermal expansion due to decreasing oxygen nonstoichiometry variations. (C) 2004 Elsevier Ltd. All rights reserved. |
publisher |
ELSEVIER SCI LTD |
issn |
0955-2219 |
year published |
2005 |
volume |
25 |
issue |
4 |
beginning page |
489 |
ending page |
499 |
digital object identifier (doi) |
10.1016/j.jeurceramsoc.2004.03.011 |
web of science category |
Materials Science, Ceramics |
subject category |
Materials Science |
unique article identifier |
WOS:000226924100022
|
ciceco authors
impact metrics
journal analysis (jcr 2019):
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journal impact factor |
4.495 |
5 year journal impact factor |
4.283 |
category normalized journal impact factor percentile |
98.214 |
dimensions (citation analysis):
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altmetrics (social interaction):
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