Effect of electrode polarisation on the determination of electronic conduction properties of an oxide ion conductor

The p-type electronic conduction parameter p⊕ of Gd0.85Ca0.15AlO3−δ, 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⊕ values that are corrected for the electrode polarisation. At lower measuring temperatures, the value of p⊕ was found to be to be time-dependent. p⊕ increased by an order of magnitude when the specimen is kept at 650 °C over a period of 1500 h.