The p-type electronic conduction parameter p(circle plus) of Gd-0 Ca-85(0) 15AlO3-delta a predominantly oxide ion conductor has been determined as a function of temperature by simultaneously taking into account the results of oxygen permeation and cell potential difference measurements under various oxygen partial pressures in the surroundings of the ceramic electrolyte Using a non-linear optimization procedure applied to the experimental data the polarisation resistances at anode and cathode can be quantified separately which allows to obtain p(circle plus) values that are corrected for the electrode polarisation At lower measuring temperatures the value of p(circle plus) was found to be to be time-dependent p(circle plus) increased by an order of magnitude when the specimen is kept at 650 degrees C over a period of 1500 h (C) 2010 Elsevier Ltd All rights reserved