IMPEDANCES OF MEMBRANE SYSTEMS WITH METAL AND OR IONIC CONTACTS

Two active interface liquid, semi-solid and glassy systems include ion conductors and mixed electron/ion conductors. Their impedance spectra have been studied since about 1965 and the results complement the slightly better documented spectra of ionic solids. A systematic survey of ion exchanger types, and mixed conductor types is presented. The kinds of cells use ion contacts, electronic contacts or one of each, and the impedance spectra show characteristics of the symmetry of asymmetry of the contacts. Equivalent effects in voltage step and voltage can experiments produce an interesting correlation with impedances. The common impedance features; bulk geometric, surface kinetic, finite Warburg with dc resistance, and finite Warburg with pure dc capacitance are analysed for these mainly unsupported systems. Impedances are then related to electrochemical characteristics, especially described by coupled ion (Nernst-Planck) or coupled ion/electron hopping in the films or membranes and the contact arrangement. Apparent interfacial ion kinetic sources and their effects are described together with single interface impedance measurements to isolate kinetic processes at one interface, that would otherwise be coupled with processes at the second interface of normal two-sided films and membranes. © 1990.