4 POINT HEBB-WAGNER POLARIZATION METHOD FOR DETERMINING THE ELECTRONIC CONDUCTIVITY IN MIXED IONIC ELECTRONIC CONDUCTORS

A four point Hebb-Wagner polarization method is analyzed. The original analysis by Wagner applies to a two-electrode configuration. The purpose of the present method is to allow the determination of the partial electronic (electron/hole) conductivity, sigma(el), of a mixed ionic-electronic conductor, MIEC, excluding the adverse effect of electrode overpotential. We discuss both a linear configuration, and a van der Pauw-type configuration with cylindrically shaped samples. The method of determining sigma(el) is presented. It is shown that the nature of the electrodes, whether ion blocking or non-blocking, is important, and that a four-electrode arrangement eliminates the adverse effect of overpotential at the current-carrying electrodes only by proper choice of all electrodes. The nature of the dominant electronic defects (electrons or holes) is determined from the ratio of the voltage drop between the various electrodes.