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

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 similar to 10(16)-10(17) cm(-3) are sufficient to make space-charge effects the dominant contribution to the decay of the ITIC at low applied electric fields (similar to 10(4) V/cm). Hence such effects should be taken into consideration when the ITIC method is used to determine conduction parameters. (C) 2001 American Institute of Physics.