Ferroelectric relaxor terpolymers: properties and potential applications

Ferroelectric materials are intrinsically multifunctional and have found a broad range of applications. A new class of semicrystalline terpolymers comprising vinylidene fluoride (VDF), trifluoroethylene (TrFE), and 1,1-chlorofluoroethylene (CFE), were prepared at ISL via a suspension polymerization process. A cooperative research program between our laboratories has led to extensive characterization and understanding of many compositions of these new relaxor terpolymers. Relevant studies and results show that this class of electroactive polymers offers unique properties in comparison with other ferroelectric polymers. The terpolymer exhibits high electrostrictive strain (>7%) with relatively high modulus (>0.3GPa). It has been also observed that the large electrostrictive strain is nearly constant in the temperature range from 20 °C to 80 °C. The high room temperature relative dielectric constant (∼50, which is the highest among all the known polymers), high induced polarization (∼ 0.05 C/m²), and high electric breakdown field (>400 MV/m) lead to very high volume efficiency for the electric energy storage operated under high voltage (∼10 J/cm³). It should be pointed out that large entropy change associated with the polarization change in the material has been observed.