Some considerations of the enhancement of ion migration in polymers under AC stress

The authors consider a theoretical model describing the migration of ions in a solid dielectric under the influence of an applied AC stress. In this model, it is considered that ionic motion is a hopping process between adjacent ion-trapping sites and that an ion experiences changes in its potential energy as it moves through the solid. The general model shows that in a solid where there exists a flux of ions driven by a local gradient in the concentration the application of an AC field will enhance any component of this which is parallel to the field, irrespective of the polarity of the ionic charge. Furthermore, if the applied field is nonuniform then the model shows that there will be an additional component of the flux of ions in the direction of decreasing field strength. The authors consider the practical case where the concentration gradient, the applied field, and the field gradient are all parallel.<>