The application of a dipolar theory to the piezoelectricity in vinylidene fluoride–co-tetrafluoroethylene polymers

Abstract

The piezoelectric activity of eight vinylidene fluoride–co-tetrafluoroethylene polymers was studied to further our understanding of this phenomenon. Film compliance, density, degree of crystallinity, and piezoelectric activity were measured in this study. It is shown that the piezoelectric d constant is calculable from a molecular dipole theory where the polarization is derived using a cavity reaction field.

Compositional variation of the structure and solid-state transformations of vinylidene fluoride/tetrafluoroethylene copolymers

“…(c) VF2 Content between ~82 and 72 mol %. In this compositional region, the behavior is characterized by reversible Curie transitions in the manner described previously.1,7 This may be seen in Figure 7 for a 79 mol % Figure 5. X-ray diffractograms at the indicated temperatures, obtained during (a) heating and (b) cooling of a VF2/F4E copolymer containing 89 mol % VF2.…”

From Vinylidene Fluoride (VDF) to the Applications of VDF-Containing Polymers and Copolymers: Recent Developments and Future Trends

“…Earlier, Lando and Doll noted that these copolymers were able to crystallize from the melt with the unit cell of the ferroelectric β phase, provided that they contained at least 7 mol % TFE. Piezoelectricity and pyroelectricity in poly(VDF- co -TFE) copolymers have been investigated by several authors . Lovinger et al synthesized poly(VDF- co -TFE) copolymers over a full compositional range and their crystalline structures were studied at ambient temperature, as well as during heating to the melting point and subsequent cooling.…”

Piezoelectric Polymers

“…In their paper, they found the expression for the hydrostatic coefficient. Later, this theory was extended and an equation for d3j was obtained (44,45). By differentiating equation (11) above and modifying it to account for dimensional effects such as in the case of stretching (44, 46)…”