EVALUATION OF TRANSPORT PARAMETERS IN THE PRESENCE OF DEFECTS WITH VARIABLE CHARGES

(i) Referring to different phenomenological levels of description the paper shows how the classical Wagner concept has to be modified with respect to diffusion equations and with respect to the meaning of the diffusion coefficients ionically and electronically conducting defects are present which may interact with each other. Substantial modification is necessary in the case of coupling of electronic and ionic-charge carries i.e. if valence changes occur. (ii) In this case the well-known electrochemical techniques have to be evaluated differently. This is shown for the examples of chemical relaxation, Wagner-Hebb polarization and concentration cell experiments. (iii) Considering different scientifically and technologically relevant examples, the importance of the theoretical results is illustrated.