This paper describes the electrode and oxygen permeation properties of Sm-doped CeO2-MFe2O4 composites prepared on a Sm-doped CeO2 electrolyte, where M = Co and Mn. The porous and thin-film samples were prepared by means of citrate-based liquid-mix and chemical solution deposition techniques, respectively. For Cole-Cole plots of porous and thin-film electrodes, two semi-circles corresponding to interface and chemical impedances were observed. The thin-film electrode of 1-mu m-thick (Ce0.9Sm0.1)O-2-30 vol.%CoFe2O4 (30CFO) composites showed a current density of 509 mA/cm(2) at 900 degrees C under a cathodic overpotential of 159 mV The 30CFO thin film exhibited an oxygen flux density of 1.3 mu mol/cm(2) s at 900 degrees C under PO2 of 1.2 x 10(-20) atm. (c) 2006 Elsevier B.V All rights reserved.