The Kinetic Behaviour of Polycrystalline Alloy Electrodes (σ‐(Fe, Zn))

The equation for the impedance of alloy electrodes was developed on the basis of a model for diffusion in polycrystalline alloys by using Fourier transformation and was included in the total cell impedance. In order to obtain experimental confirmation, the magnitude and the phase displacement of the impedance of cells containing electrodes made of Γ(Fe,Zn) were measured with the aid of a special impedance spectrometer. The experimental results were very well represented by the theoretical equation in the frequency range from 0.3 Hz up to 7 kHz. The evaluation yielded the electrochemical parameters of the alloy electrode. Thus, the coefficients D(25 °C) = 2 · 10−16 cm2 s−1 of bulk and D' (25 °C = 5 · 10−8 cm2 s−1 of grain boundary diffusion, as well as their activation energies were determined.