SOFC-anodes, proof for a finite-length type Gerischer impedance?

The impedance of a symmetric cell with Ni/Ti-doped YSZ cermet anodes was measured as function of ambient (PH2, PH2O) and temperature. The impedances showed identical shapes with a minor dispersive contribution in the high frequency region and a dominating dispersion down to 0.01 Hz. The characteristic shape of this dispersion was clearly in between a finite-length Warburg (FLW) and a Gerischer impedance. Analysis of the dispersion in the Bode representation, after subtraction of the high frequency contribution, showed a clear relation with the Gerischer impedance. Assuming a finite-length constraint led to quite reasonable modelling of the data. The parameter set of this finite-length Gerischer showed a consistent dependence on PH2, PH2O. A qualitative interpretation of this modified Gerischer is presented.