The self-diffusion coefficient (D*) and oxygen surface exchange coefficient (k) for La0.6Sr0.4Co1-xNixO3-delta (LSCN, where x = 0.02) were measured over the temperature range 400-700 degreesC using Isotopic Exchange Depth Profile and Secondary Ion Mass Spectroscopy techniques (IEDP/SIMS). From this, the activation energy for oxygen diffusion was calculated to be 134 kJ/mol. In addition, the electrochemical impedances of porous LSCN and composite LSCN/Ce0.9Gd0.1O1.95 (CGO) cathodes were measured by AC impedance spectroscopy. Adding ionic conducting CGO to the mixed conducting LSCN was found, to a certain extent, not to have an adverse effect on electrode properties. (C) 2000 Elsevier Science B.V. All rights resented.