Pyroelectrical study of the polarization contributions from the amorphous and crystalline phases as well as from their interface in poly(vinylidene fluoride)

With new selective poling schemes for polar semicrystalline polymers (poling temperatures below and/or above the glass-transition temperature as well as poling fields lower and/or higher than the coercive field), it is possible to clearly separate the respective contributions to the polarization in poly(vinylidene fluoride). From dynamic pyroelectrical measurements, the permanent polarization of the dipoles in the crystalline phase, the frozen-in polarization of the dipoles in the amorphous phase and the effect of the excess charges of the Maxwell-Wagner interface (MWI) polarization can be identified. In addition, the depth profiles of the polarization after various poling schemes have been investigated with the Laser-Intensity Modulation Method (LIMM). It is found that the more or less uniform bulk polarization does usually not extend to the electrodes and that there are depolarization zones near the electrodes