High voltages in the preparation, operation and application of electrets

Abstract

High electric fields and thus often also high voltages are required for the electrical charging of polymeric spacecharge electrets (in particular, if charge injection is required), for the electrical poling of piezo-, pyro- and ferroelectric polymer electrets (in particular, if the respective coercive field needs to be overcome or if the material is in a glassy state), for the electrical charging/poling of polymer ferro- or piezoelectrets by means of dielectric barrier discharges (in particular, as the respective threshold field for Paschen breakdown needs to be overcome), and for the electrical poling of piezo- and pyroelectric ceramicpolymer composites (in particular, as the respective coercive fields need to be reached). Especially on dielectric elastomers or electro-electrets and on relatively thick polar-polymer electrets, the voltages required for the successful operation of actuating devices may be in the lower kilovolt range with electric fields of up to a few hundred megavolts per meter. Last, but not least, electrets may be used as sensor materials in high-voltage and high-field environments so that they should be able to withstand high-voltage pulses or transients. In several of the above-mentioned cases, the required voltages or electric fields are close to or even above the respective thresholds for electrical breakdown. Therefore, electrets may be regarded as an example for potentially useful effects of high voltages and high fields on dielectric materials.