Significant enhancement of the charging efficiency in the cavities of ferroelectrets through gas exchange during charging

Ferroelectrets are non-polarpolymer foams orpolymer systems with internallycharged cavities. They arecharged through a series ofdielectric barrier discharges (DBDs) that are caused by the electrical breakdown of the gas inside the cavities. Thus, the breakdown strength of the gas strongly influences thecharging process of ferroelectrets. A gas with a lower breakdown strength has a lower threshold voltage, thus decreasing the onset voltage for DBDcharging. However, a lower threshold voltage also leads to a lower value for the remanentpolarization, as back discharges that are caused by theelectric field of the internally depositedcharges can take place already at lowercharge levels. On this basis, acharging strategy is proposed where the DBDs start in a gas with a lower breakdown strength (in the present example, helium) and are completed at a higher breakdown strength (e.g., nitrogen or atmospheric air). Thus, the exchange of the gas in the cavities duringcharging can significantly enhance thecharging efficiency, i.e., yield much higherpiezoelectric coefficients in ferroelectrets at significantly lowercharging voltages.

Source: Applied Physics Letters - December 1, 2016 Category: Physics Authors: Xunlin Qiu Source Type: research