A GENERAL-APPROACH FOR PREDICTING ELECTRIC BEHAVIOR, IN THE PRESENCE OF CONDUCTING FILMS WITH AN EXAMPLE OF GROWING FILM WITH NERNSTIAN REACTIONS

In view of further applications to various kinds of electric systems i nvolving a solid film between two solid phases, a general approach is proposed for treatments which can predict the electric behavior in the steady state and then, with superimposition of d.c. and a.c. potentia ls, given a specific 'reaction'' scheme. This approach is illustrated by the treatment of a model that leads to the growth of a film on a me tal in contact with an electrolytic solution. The charge carriers in t he film are assumed to be ionic vacancies. Using the reaction scheme c hosen, the film grows at its two interfaces. If all the reactions are Nernstian, the vacancy concentrations in the growing film remain const ant and equal during the growth and the instantaneous current varies i n proportion to the applied steady potential. Adding the assumption of a chemical dissolution of the film at the electrolyte side to the mod el, the formation of a steady film whose thickness is in proportion wi th the steady potential is simply explained. These simple models may e xplain behaviors observed in the past and in more recent experiments. More complex behaviors may be predicted when the reactions are not Ner nstian, when the film is not neutral, and/or for other kinetic schemes . The application of this approach in the treatment of other systems o f interest in various fields (including those with three solid phases) is also proposed.