Slow steady transport by mixed ionic-electronic conductors: Electrochemical oxygenation of La2CuO4+x and La2NiO4+x
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abstract
Mixed ionic-electronic conductors have both ionic and electronic charge carriers, whose relative importance for electrical transport depends upon the boundary conditions imposed on the charge carriers by the electrodes. Timely examples are (Formula presented) and (Formula presented) When these systems are oxygenated electrochemically, oxygen enters as (Formula presented) at one electrode and holes enter at the other electrode. For slow steady transport, the electric field, rather than being uniform, varies linearly across a cylindrical sample. For pairs of electrodes that pass only holes or only (Formula presented) ions, the electric field is uniform, but the steady-state conductivity is not that due to pure conduction by the charge carrier; it is enhanced by diffusion of that charge carrier. The short-time, or ac, conductivity is independent of the electrodes and is the sum of the individual charge-carrier conductivities. 1999 The American Physical Society.
