The electrochemistry of mixed conductors is outlined. In particular the impact of grain boundaries on the transport perpendicular to the grain boundary plane is studied. Fe-doped SrTiO3 bicrystals were used as prototype mixed conductor. Experimental results obtained by
optical spectroscopy (chemical diffusion) and electrochemical impedance spectroscopy (electrical transport) are analysed in terms of continuum models. A unified approach based on the use of “chemical capacitors” is briefly explained. For the description of grain boundary, the
Schottky model acting on electronic and ionic charge carriers is used
