ABSTRACT
The electret effect in solid-state physics has attracted a great deal of attention on account of its numerous practical applications. The electret is popular for device applications because of its small size and weight, and also due to its very long lifetime of surface charge. An electret is a solid dielectric piece polarized by the simultaneous application of an electric field and heat. Electrets are usually prepared by cooling a heated dielectric in a strong electric field, following the technique of discoverer of the electret, Mototaro Eguchi 1-4]. Th sample e txhibits electrical charges of opposite signs on its two sides. Electrets are considered as counterparts of magnets. They are metastable, and their polarization decays slowly with time after the termination of the polarization treatment. The persistance and the magnitude of polarization, however, depend on a number of factors, such as the material used for the preparation, the magnitude of the polarizing field, the polarizing temperature, polarization time, thickness of the sample, electrode material, etc. Michael Faraday was the first to outline the basic principles of the electret when he published Experimental Researches in Electricity. Oliver Heviside coined the word "electret" to describe dielectric bodies which retain their electric moments even\ after the externally applied electric field has been reduced to zero [3].
