Piezoelectric Effect in Stretched and Polarized Polyvinylidene Fluoride Film

The mathematical expressions for the piezoelectric stress-constant, the electrostrictive constant, and the dielectric constant, all as complex quantities, have been derived by means of non-equilibrium thermodynamics on the assumption that the dipole orientation produces a residual polarization. The temperature dependence of these quantities for electretized polyvinylidene fluoride films has been experimentally determined at a frequency of 20 Hz over the temperature range from -100°C to 100°C. The residual polarization calculated from these experimental data is of the order of 10 3 esu/cm 2 . This polarization presumably originates from the aligned dipoles associated with the crystalline region. Measurements during poling process show a gradual two-step increase of the residual polarization.