Piezoelectric response in trifluoroethylene copolymers of vinylidene fluoride

Abstract

The copolymer system of polyvinylidene fluoride-trifluoroethylene, P(VDF-TrFe), has been shown to exhibit a Curie temperature Tc that is dependent upon the monomer ratio. Below this temperature the copolymer is in a ferroelectric phase similar to the stretched homopolymer, Polyvinylidene fluoride, PVDF. The piezoelectric response of this copolymer system for oriented, well-poled samples is very similar to and in some cases better than PVDF. Again the piezoelectric response may also depend upon the monomer ratio. However, when the copolymer with a monomer ratio of 3/1 for VDF/TrFE is poled above Tc and subsequently annealed it has an exceptionally high percentage crystallinity and an electromechanical coupling coefficient of 0.3. These values are for undrawn samples and can be used to predict a hydrostatic piezoelectric response approximately two to three times better than PVDF. These concepts and possible new data will be presented.