Experimental limitations in impedance spectroscopy: Part III. Effect of reference electrode geometry/position

Experiments and computer simulations on Pt/YSZ specimens in various electrode configurations were performed to investigate the effect of reference electrode geometry/position on the accuracy of impedance measurements. The internal, Luggin probe-type, geometry is the preferred reference electrode configuration as it accurately measures both electrolyte and electrode impedances. External, ‘pseudoreference’, electrodes sample an averaged effective potential and can register inaccurate electrolyte resistances, sometimes with distorted electrode arcs. A symmetric configuration can accurately measure the impedance of an electrode; however, the electrolyte resistance will not scale linearly according to sample dimensions, as one might expect. An asymmetric configuration exhibits both non-linear partitioning of electrolyte resistance and distortions in the electrode impedance arc under certain circumstances. The reliability of three-electrode measurements is very sensitive to aspect ratio and electrode configuration.