Dipolar orientation and hysteresis in polyvinylidene fluoride

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Abstract
Dielectric hysteresis of stretched polyvinylidene fluoride films under a sinusoidal electric field of a period of 300 sec with an amplitude of 240 MV/m is observed by the aid of a minicomputer. It is found that the coercive field is about 50 MV/m and the remanent polarization is about 65 mC/m2. The dipolar polarization initially present in the sample is determined from the shape of the hysteresis loop for the first cycle. If the poled film is annealed at 100 °C for 1 h, the hysteresis loop becomes distorted for the first cycle, but returns to the normal shape after two or three cycles. The linear relationship between the residual dipolar polarization and the piezoelectric stress constant is determined.