Incorporation of nickel into the iron sublattice of LaFeO3-delta was found to result in increasing oxygen nonstoichiometry, electrical conductivity, and thermal expansion of the perovskites. Activation energy for electrical conductivity of the LaFe1-xNixO3-delta (x = 0.2-0.5) decreases with x in the range from 23.9 to 6.6 kJ/mol. Thermal expansion coefficients of the ceramic materials calculated from the dilatometric data were (8.9-11.9) x 10(-6) K-1. Oxygen permeation through LaFe1-xNixO3-delta membranes was found to increase with nickel content due to increasing oxygen vacancy concentration and bulk ionic conductivity, which are the permeation flux-limiting factors.