Evolution of electret applications

Abstract

Charge storage or polarization phenomena in dielectrics can be associated with two types of effects. Indeed, a frozen polarization or trapped charges can either induce internal effects or create an external electric field. In the first case, the physical properties of the material can be modified leading for instance to piezoelectricity or to nonlinear effects. In the second case, an external electric field of large magnitude can be created. The author recalls the evolution which took place for both types of electrets and associated applications.