Phase formation and iron oxidation states in SrFe(Al)O3-delta perovskites


Mossbauer spectroscopy, total conductivity measurements and X-ray diffraction (XRD) have been used to evaluate phase formation and Fe oxidation and coordination states in the Sr(Fe1-xAlx)O3-delta system. A solid-solution range of cubic perovskite (ABO(3)) with random B-cation distribution forms in the approximate limits, 0 <= x <= 0.35. The Fe3+/Fe ratio increases with increasing Al concentration fomenting a B-O network with isolated Fe4+ species, resulting in p-type electronic conductivity via a hopping mechanism. The activation energy for hole transport, 28-30 kJ/mol at 300-700 K in air, exhibits little variation with x. Thermal expansion coefficients, (13.5-16.4)x 10(-6) K-1 at 373-923 K and (18.6-31.9)x 10(-6) K-1 at 923-1273 K, decrease with increasing Al content and oxygen nonstoichiometry. (c) 2005 Elsevier B.V All rights reserved.



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Materials Science; Physics


Waerenborgh, JC; Rojas, DP; Shaula, AL; Mather, GC; Patrakeev, MV; Kharton, VV; Frade, JR

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