Electromechanical properties of composite electret structures

Summary form only given, as follows. A generalised thermodynamical model of composite electret structures is presented. In case of excess charge electrets in series with linear dielectrics, this model allows computation of the composite dielectric and mechanical properties, as well as the linear piezoelectric and pyroelectric effects. The electromechanical coupling coefficients and different figures of merit are computed for sensors and actuators versus parameters defining the two dielectrics and the geometry of the structure. Since this model allows the equilibrium states of the composite structure to be defined, the conditions for electromechanical bistability are easily deduced.<>