The effects of reannealing on the depolarization and phase transition behaviors of poled ferroelectric copolymer film of P(VDFndash;TrFE) (75/25) are studied by using differential scanning calorimetry (DSC) and piezoelectric resonance techniques from a viewpoint of formation of ferroelectric domains. It is found that the DSC peak at Curie point (Tc) splits into two peaks by reannealing at temperatures aroundTc, the broader one appearing at a lower temperature and the sharper one at a higher temperatureTcH. As the annealing temperature increases, the peak atTcHshifts to the higher temperature side, and its peak intensity decreases less rapidly than the macroscopic polarization of the film. To explain these phenomena we propose that ferroelectric domains possibly composed of 60deg; and 180deg; domains are developed within lamellar single crystals during the reannealing process at temperatures aroundTc.
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