Dielectric material with a permanent or quasi-permanent electric dipole.
Notes: - A real-charge electret is obtained by the charge carrier injection onto the surface or into a parent dielectric material. It may contain either positive or negative excess charges or both, which must be trapped so that a good insulating parent dielectric material such as a fluoropolymer must be used.
- An oriented-dipole electret is obtained by poling a parent dielectric material with dipolar groups at a temperature above the glass transition temperature \(T_{\rm{g}}\), and eventual next stabilization of the structure by cooling the electret down below \(T_{\rm{g}}\) or by crosslinking.
- Electrets are electric equivalents of magnets; electric magnets. Some oriented-dipole electrets are ferroelectric polymers and piezoelectric polymers. Quartz is an example of the natural electret.
Source:
PAC, 2022, 94, 15. 'Glossary of terms relating to electronic, photonic and magnetic properties of polymers (IUPAC Recommendations 2021)' on page 25 (https://doi.org/10.1515/pac-2020-0501)