Coupling between ionic and electronic fluxes in mixed ionic/electronic conductors: experiments on Co1-δO

In investigations of the isothermal transport properties of mixed conductors the dynamical coupling between ionic and electronic partial fluxes is usually neglected. Within the formalism of (linear) irreversible thermodynamics this assumption is expressed by a vanishing cross coefficient L12 in the matrix of the phenomenological transport coefficients. By analysing the phenomenological flux equations for cation vacancies and electron holes, experiments for the determination of the cross coefficient are defined. Experimental results for the coupling effect in Co1-δO are presented, which have been obtained from three independent techniques. The results are discussed in the light of previous theoretical considerations. It is shown that a strong coupling between cation vacancies and electron holes exists in the case of Co1-δO. To account for this coupling, an effective charge number of ions has to be introduced for use in the formulation of ionic fluxes. (orig.)