Effect of iron substitution content on structure, thermal expansion behavior and electrochemical properties of La0.5Ba0.5Co1-yFeyO3-δ

Cubic perovskite oxides La(0.5)Ba(0.5)Co(1-y)Fe(y)O(3-delta) (LBCF-y) with Fe content y = 0.1-0.7 were synthesized by sol-gel method and were studied with respect to their oxygen content, defect chemistry, thermal expansion behavior, and electrical and electrochemical properties. LBCF-y had increased oxygen content and cell volumes with higher Fe content. The chemical defects at B-sites of LBCF-y are Fe(4+), Co(4+) and Co(3+) ions for y = 0.1-0.3, and Fe(4+), Fe(3+) and Co(3+) ions for y >= 0.5 respectively. Thermal expansion coefficients of LBCF-y oxides firstly increased to a maximum at y = 0.3 then decreased gradually with bigger y. Conductivities of LBCF-y decreased with higher Fe content, and the maximum conductivity was 800 S cm(-1) at 500 K for LBCF-0.1 sample. Fe substitutions for Co in LBCF-y cathodes increase the high-frequency resistance associated with oxygen ionic diffusion process while hardly influence the low-frequency gas diffusion process. Very low area-specific resistances, <0.1 ohm crn(2) at 923 K, were obtained for LBCF-y (y = 0.1-0.7) oxides, demonstrating their potential applications as cathode materials for intermediate-temperature solid oxide fuel cells. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.