Dielectric properties of humid mica surfaces

Abstract

The dynamic behaviour of conduction and polarization processes on humid surfaces of mica has been studied in the frequency and time domains as function of the relative humidity, sample geometry, steady bias and electrode material. Detailed analysis of complex impedance and admittance plots has led to improved understanding of the role of the electrodes. The general conclusion which confirms and augments earlier studies is that humid mica surfaces may be represented by a parallel combination of an essentially extraneous “electrode capacitance” which does not depend on humidity and bias, and the surface processes which ultimately become dominated by low-frequency dispersion. It is concluded that the behaviour does not depend in a major way on the nature of the electrode material, which implies that the dispersive processes observed are intrinsic to the humid surface, and are not dominated by contact effects between the metal contacts and the humid surface.