Characterization of Ln0.5M0.5FeO3-δ (Ln = La, Nd, Sm; M = Ba, Sr) perovskites as SOFC cathodes

Ln(0.5)M(0.5)FeO(3-delta) (Ln = La, Nd, Sm; M = Ba, Sr) perovskites have been synthesised by the glycine-nitrate route in order to obtain compounds with good morphological and electrical characteristics to be used as SOFC cathodes. A systematic study of the influence of the average ionic radius of the A cation (<r(A)>:), on the structural, morphological and electrical properties of these perovskites has been performed. The obtained materials have been characterised by ICP-AES analysis, X-ray powder and neutron powder diffraction, scanning electron microscopy and four-probe conductivity measurements. In this study <r(A)> has been changed in the range 1.34 >= <r(A)> >= 1.25 angstrom(2), while keeping constant the doping level, x = 0.5 (in A position) and A cation size disorder, sigma(2) (r(A)) = 0.0161 angstrom(2). Overall, the sample with the higher average ionic radius showed the highest values of conductivity. Chemical compatibility of the proposed cathodes with yttria-stabilised zirconia electrolyte (YSZ) has also been analysed. The data indicate that additional phase formations exist in all systems at temperatures above similar to 1000 degrees C. (C) 2011 Elsevier B.V. All rights reserved.