Electrical and electro-chemical characterisation of La0.99Fe1-xNixO3-δ perovskites

La0.99Fe1-xNixO3-delta (LFN, 0 < x < 0.6) perovskites were synthesised by a solid-state route and were characterised by powder XRD, dilatometry, four-point DC conductivity measurements and electro-chemical impedance spectroscopy (EIS) on cone-shaped electrodes using a Ce1.9Gd0.1O1.95 (CGO10) electrolyte. All the compounds were of single phase, and they belong to either the cubic or the hexagonal crystal system. The thermal expansion coefficient (TEC) was in the range 10.7* 10(-6) K-1 to 13.4* 10(-6) K-1, which continued to increase with increasing nickel content. The highest electronic conductivity was measured for the composition La0.99Fe0.4Ni0.6O3-delta, giving a value of 670 S/cm at 380 degrees C. The highest electrochemical performance was measured for the composition La0.99Fe0.4Ni0.6O3-delta giving an area specific resistance as low as 5.5 Omega cm(2) at 600 degrees C based on EIS measurements on a cone-shaped electrode. Composite cathodes made from La0.99Fe0.4Ni0.6O3-delta and CGO10 revealed a rather low performance due to an un-optimised micro-structure.