Switching Phenomena in Vinylidene Fluoride / Trifluoroethylene Copolymers near the Curie Point

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Abstract
Ferroelectric switching and dielectric relaxation processes were simultaneously observed by a time-domain measurement of charge responses induced by a step voltage for a 65/35 mol% copolymer of vinylidene fluoride and trifluoroethylene. These processes were separated on the basis of the different field dependences of their characteristic time constants and resulting polarization changes. As the temperature approaches the Curie Point (T c∼68°C), both the activation field and the amount of reversed polarization associated with the switching process fall to zero. It is found that the switching times under various fields converge to the relaxation time at T c. This result implies that the switching process is affected by dipole fluctuations, probably at an early stage when the nuclei of reversed domains are created.