Impedance characteristics of oxide layers on aluminium

The electrochemical behavior of oxide layers on aluminium was studied using electrochemical impedance spectroscopy. Impedance spectra were taken at a compact and a porous oxide layer of Al. The anodic films on Al have a varia ble stoichiometry with gradual reduction of oxygen deficiency towards the o xide-electrolyte interface. Thus, the interpretation of impedance spectra f or oxide layers is complicated, with the impedance of surface layers differ ing from those of ideal capacitors. This layer behavior with conductance gr adients was caused by an inhomogeneous dielectric. The frequency response c annot be described by a single RC element. The oxide layers of Al are prope rly described by the Young model of dielectric constant with a vertical dec ay of conductivity.