Nonuniform polarization of vinylidene fluoride-trifluoroethylene copolymer

Polarization distribution of vinylidene fluoride (VDF)-trifluoroethylene (TrFE) copolymer is studied. X-ray diffraction spectra and pyroelectric light detecting responses of the films, polarized by dc electric field, suggested extremely nonuniform polarization in the direction of the field. That is, the positively poled surface was well polarized and the negatively poled surface was little polarized. A calculation based on a stepwise polarization distribution model showed that the polarization depth of the 75-μm films was 45% of the film thickness, and that the pyroelectric coefficient of the polarized surface was 9 nC/cm2 K, when the films were polarized by dc 20 kV/mm at 100 °C for 1 h.