Structural, electronic and transport properties of LFN (LaFe1-xNizO3) and LSCFN (La1-xSrxCo1-y-zFeyNizO3) perovskites synthesized by a modified citric acid method were studied. Structure of the samples was characterized by X-ray studies with Rietveld method analysis. Magnetic properties and valence states of iron ions were characterized by Fe-57 Moessbauer spectroscopy performed at RT, which were found to be greatly dependent on the chemical composition of the samples. Electrical conductivity was measured in the 20-800 degrees C temperature range and for some compositions relatively high values (exceeding 100 S cm(-1)) were observed in the 600-800 degrees C range. Chemical stability studies in relation to Ce0.8Gd0.2O1.9 electrolyte, performed for selected perovskite samples, revealed decreasing stability with increasing Ni concentration and formation of solid solutions in CGO/perovskite composites. The coefficient of thermal expansion (CTE) of LFN perovskites was found to match that of CGO electrolyte (CTE in the 10-13 (.) 10(-6) K-1 range). (c) 2006 Elsevier B.V. All rights reserved.