THE POSSIBILITY OF FORMATION OF LARGE FERROELECTRIC DOMAINS IN A COPOLYMER OF VINYLIDENE FLUORIDE AND TRIFLUOROETHYLENE

Two Curie temperature T(c) 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 T(c). The DSC peak at higher T(c) 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-degrees or 180-degrees domains during reannealing. The free energy of the simple 180-degrees domain model is used to discuss the temperature dependence of T(c) 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 T(c) irrespective of its macroscopic polarization.