Theoretical derivation of the isothermal transient ionic current in an ion conductor: Migration, diffusion, and space-charge effects

Abstract

The Green’s function technique was used to determine the isothermal transient ionic current (ITIC) caused by the application of a constant potential across an ion conductor which initially contained the ions under consideration. The analysis included migration, diffusion, and space-charge effects as contributions to the ionic motion. Furthermore, the relative importance of diffusion and space-charge effects as current limiters was investigated. It was found that ion concentrations as low as ∼1016–1017 cm−3 are sufficient to make space-charge effects the dominant contribution to the decay of the ITIC at low applied electric fields (∼104 V/cm). Hence such effects should be taken into consideration when the ITIC method is used to determine conduction parameters.