The Effect of Crystal Polymorphism of Ferroelectric Copolymer Vinylidene Fluoride‐hexafluoropropylene on Its High‐voltage Polarization

Dielectric response of vinylidene fluoride-hexafluoropropylene copolymer, crystallized in different polymorph modifications, to a high-voltage electric field was studied. Polarization switching at high electric fields below coercive was detected. It was found that crystallization of the copolymer predominantly in nonpolar alpha-phase is accompanied by more intensive growth of electric displacement at polarization. For the sample with higher content of polar gamma-phase, the value of high-voltage conductivity "anomalously" decreased with increasing field at fields above coercive. The data on the field dependences of the remnant polarization showed that this should be attributed to an increase of the effective capture cross section of deep traps of gamma-phase polar planes for impurity and injected carriers. X-ray diffraction has revealed the field-induced transition of a part of the chains of the amorphous phase to the crystal.