Electrostriction-enhanced giant piezoelectricity via relaxor-like secondary crystals in extended-chain ferroelectric polymers*

Piezoelectricity in ferroelectric polymers originates from the electrostrictive effect coupled with a remanent polarization. However, its structural origin remains controversial, and it is not clear how modifying the electrostriction can further improve piezoelectricity for polymers. Here, we report that electrostriction can be significantly enhanced in poled poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] random copolymers containing extended-chain primary crystals and relaxor-like secondary crystals in the oriented amorphous fraction (SC_OAF). As a result of the high polarizability of dipoles and ferroelectric nanodomains in the SC_OAF, the inverse piezoelectric coefficient d31 reaches as high as 77±5 pm/V for the P(VDF-TrFE) 55/45 copolymer at 55 °C. This finding not only extends our understanding of piezoelectricity in polymers, but also provides guidance for further enhancing the piezoelectricity of ferroelectric polymers in the future.