aFuel Cells and Solid State Chemistry Department, Risø National Laboratory, Technical University of Denmark, DK-4000 Roskilde, Denmark Received 21 April 2006; revised 8 May 2007; accepted 27 July 2007. Available online 27 August 2007.
Strongly A-site deficient perovskites with the composition (La0.6Sr0.4)1−sFe0.8Co0.2O3−δ where s equals 0.01, 0.05, 0.10, 0.15 or 0.20, were synthesised and characterised by powder X-ray diffraction (XRD), dilatometry, 4-point DC-conductivity measurements, and electrochemical impedance spectroscopy (EIS) on cone shaped electrodes using a Ce0.9Gd0.1O1.95 (CGO10) electrolyte. A scanning electron microscopy (SEM) study of the compounds was also undertaken. The composition (La0.6Sr0.4)0.85Fe0.8Co0.2O3−δ revealed the highest electro-catalytic activity with an area specific resistance (ASR) of 14.8 Ω cm2 at 600 °C measured on a cone shaped electrode. This was suggested to be due to a lowering of the surface segregation of La and Sr. The creation of a two-phase perovskite structure is another possible explanation for the lowered ASR. A further lowering of the A-site stoichiometry leads to a large increase in the ASR, probably due to loss of Co from the perovskite phases.