The effect of p(O2) change on work function (WF) of oxide electrode materials, such as (La,Sr)(Mn,Co)O-3 and (La,Sr)(Mn,Fe)O-3, was determined at 1073 K during oxidation and reduction. Oxidation of both LSM and LSC results in WF changes that are rate controlled by oxygen chemisorption. Replacement of Mn with Fe in LSM, results in a decrease of the chemisorption-related surface barrier to a negligible level. (C) 2000 Elsevier Science B.V. All rights reserved.