The possibility of formation of large ferroelectric domains in a copolymer of vinylidene fluoride and trifluoroethylene

Abstract

Two Curie temperature Tc peaks in differential scanning calorimetry (DSC) are observed in a well-crystallized, nonpoled film of a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene [P(VDF-TrFE)] when it is reannealed at temperatures near Tc. The DSC peak at higher Tc shifts to higher temperature with increasing reannealing temperature, the phenomenon being very similar to that observed in thermally depolarized P(VDF-TrFE) film. This result can be explained by the formation of large 60° or 180° domains during reannealing. The free energy of the simple 180° domain model is used to discuss the temperature dependence of Tc on the domain width and thickness. It is concluded that large domains are generally formed in a P(VDF-TrFE) film by reannealing at temperatures near Tc irrespective of its macroscopic polarization.