Electrets

Electrets have, over the past decade, emerged as invaluable components in an ever increasing number of applications. Their usefulness is responsible for the recent impressive growth of research work in a field which had been actively investigated since about t 920. This volume aims to present the fundamental aspects of electret research as well as a detailed review of recent work in this area. The book is broad in scope, extending from the physical principles of the field to isothermal and thermally stimulated processes, radiation effects, piezoelectric and pyroelectric pheno mena, bioelectret behavior, and, last, but not least, to applications of electrets. The emphasis of the experimental work discussed is on polymer electrets, but work performed on other organic substances, notably biomaterials, and on inorganic materials, such as ionic crystals or metal oxides, is also reviewed. The interest in polymer electrets is due to the fact that these show extremely good charge-storage capabilities and are available as flexible thin films. In the 1960s attention focussed on highly insulating polymers, such as polytetrafluo roethylene, which have deep traps that store charges for extremely long periods of time. Around 1970, discovery of the strong piezoelectric properties of polyvinylidenefluoride attracted the imagination of many researchers and an enormous amount of work was devoted to the investigation of the physical and chemical properties of this and similar materials. Today, very active research is underway on charge-storage properties of both classes of polymers.