Abstract
Combination of impedance spectroscopy and open‐cell voltage measurements has been used to determine the transport properties of mixed‐conducting electrolytes. It is clearly demonstrated experimentally that the ratio of open‐cell voltage to the applied Nernst potential can be quite different from the average ionic transference number; the effect of interfacial polarization resistance on determination of transference numbers of a mixed‐conducting electrolyte must be carefully analyzed, particularly for a cell based on a thin electrolyte, tested at low temperatures, or exposed to an atmosphere containing low activities of electroactive species.