An effect of the film texture on high-voltage polarization and local piezoelectric properties of the ferroelectric copolymer of vinylidene fluoride

Abstract

Vinylidene fluoride and tetrafluoroethylene copolymer 94/6 texturing has been carried out by one-axis drawing at Td = 75 °C up to the ratio of 6 with subsequent isometric tempering at 130 °C. Data of X-ray diffraction and IR-spectroscopy indicate partial polymorph transition from the metastable γ-phase to the polar β-modification with long segments in the conformation of the planar zigzag. The surface topography data show that the oriented film roughness turns out to be almost three times lower than that of the isotropic one. High-resolution vector piezoresponse force microscopy (PFM) has been used to investigate topography and ferroelectric domains in polymer films for visualization out-of-plane and in-plane polarization components. It is shown that, in the oriented sample, both crystallinity and the degree of polar β-phase crystal perfection are higher. It was found that conductivity “abnormal” dropping takes place at the stage of intensive Pr rising with the field growing. This fact is explained by quick trapping of charge carriers by polar planes of crystals with increasing the effective trap area.