We have determined k(ex) and D-chem for (La0.8Sr0.2)(0.99)Co0.8Ni0.2O3-delta by the use of electrical conductivity relaxation on a dense sample and by applying the ALS model to measured AC impedance spectrum on a porous electrode. Extracting k(ex) and D-chem from the methods resulted in comparable values. k(ex) and D-chem also agreed well with literature values on La0.8Sr0.2CoO3-delta, indicating that nickel substitution does not change the oxygen transport properties. k(ex) of the porous sample was further found to decrease with a five times higher rate than D-chem when measured by using an Electrochemical Impedance Spectroscopy (EIS) over several days. (C) 2009 Elsevier B.V. All rights reserved.