ElektretDielektrikum

ElektretDielektrikum refers to a dielectric material that possesses a quasi-permanent electric polarization. This polarization is analogous to the permanent magnetism of a ferromagnetic material. Unlike a temporary dielectric polarization that disappears when the external electric field is removed, an electret retains its polarization for extended periods, sometimes even years. This retained polarization arises from the alignment of permanent dipoles within the material or from space charges trapped within the dielectric.

The properties of electrets depend heavily on the material used and the method of their creation. Common materials include polymers like PTFE (Teflon), PVDF, and FEP, as well as ceramics and waxes. The polarization can be induced through various techniques, such as heating the material in the presence of a strong electric field and then cooling it down while the field is still applied (thermally stimulated polarization) or by charging the material in a corona discharge.

Electrets have found applications in various fields due to their unique electrical properties. They are employed in electret microphones, where the vibrating diaphragm causes changes in capacitance due to the electret's field, generating an audio signal. They are also used in air filters for electrostatic precipitation, in electrostatic printers, and in some types of sensors. The stability and longevity of the electret polarization are key factors determining its suitability for a particular application.