A finite element study on the influence of surface cracks on micro-contact impedance spectroscopy measurements

Micro-contact impedance spectroscopy (MCIS) is a powerful tool to analyse local features of interest in electroceramics. The surface condition of the measured area of interest however may not always be ideal. Surface defects such as cracks may be present and therefore influence the measured MCIS data, especially for a top-top electrode configuration. Here we develop a finite element model on a system where a crack of various dimensions exists on the top surface between two surface micro-contact electrodes. We show how a crack can influence the current distribution within the sample and its effect in evaluating the MCIS data and associated extracted conductivity values. When the micro-contact separation is low, the hindrance effect forming from a crack acts to counterbalance the strong current interference effect that originates from closely placed top-top electrodes. The crack depth and length prove to be more effective than crack width in terms of counterbalancing interference. As the micro-contact separation increases, both current interference and crack hindrance decreases. Cracks in a specimen may therefore fortuitously assist in offsetting significant current interference effects, especially at the micro-contact separations used in many experimental set-ups.