Ferroelectric properties of poly(vinylidene fluoride-tetrafluoroethylene)

Abstract

Ferroelectric hysteresis of a copolymer of vinylidene fluoride with tetrafluoroethylene and of uniaxially stretched polyvinylidene fluoride has been observed at 60 Hz at room temperature. The measured remanent polarization of the copolymer was in good agreement with a calculated value using a frozen dipole model and measured piezoelectric coefficients. The dielectric constant for the copolymer has been measured at 1000 Hz as a function of temperature. Also, a set of copolymer films of varying thickness were poled above the melt temperature and their piezoelectric stress coefficients g₃₁ were measured as a function of the poling field. These measurements indicate that the copolymer, when poled above the melt temperature, exhibits bulk polarization. These results suggest that this copolymer is ferroelectric and that poling aligns the dipoles in the β crystal phase of the material.