Conductivity Induced Polarization in a Semicrystalline Ferroelectric Polymer

摘要

It is commonly believed that formation of polarization and its switching in ferroelectrics under high electric field strength is a fast process in the microsecond range governed by a well known activation field. We have found, however, that in semicrystalline ferroelectric polymers, containing both crystalline and amorphous phases, polarization continues to grow during times 5 to 6 orders of magnitude longer than the estimated switching times. The controversy has been resolved by taking into account the effect of conductivity in such materials. It has been shown that there are two components of the ferroelectric polarization, of which the first one is essentially field dependent and originates from a fast alignment of dipoles in crystalline regimes, while the second slow component is controlled by the conductivity of the material. Appropriate modeling showed that charge accumulation at the interfacial boundaries is an important component of the slow polarization. Good agreement between calculated and measured polarization has been observed for poly(vinylidene fluoride) (PVDF). However, it is believed that the phenomenon is probably common for all two-phase ferroelectrics such as ceramics and ceramics-polymer composites.