Influence of superimposed direct voltage on the a.c. dielectric properties of some dielectrics

Changes in the a.c. dielectric properties of inhomogeneous insulating materials in the presence of a superimposed direct voltage are analysed and explained on the basis of a model consisting of a simple sandwich capacitor, taking into account not only macroscopic dielectric properties, but also the behaviour of the charge carriers involved. The classical Maxwell-Wagner treatment is therefore modified to take account of a possible variation of charge-carrier density caused by superimposed direct voltage, with a consequent dependence of a.c. permittivity and dielectric loss on the superimposed direct voltage.