Enhanced piezoelectricity from highly polarizable oriented amorphous fractions in biaxially oriented poly(vinylidene fluoride) with pure β crystals

Piezoelectric polymers hold great potential for various electromechanical applications, but only show low performance, with |d(33)|< 30 pC/N. We prepare a highly piezoelectric polymer (d(33)=-62 pC/N) based on a biaxially oriented poly(vinylidene fluoride) (BOPVDF, crystallinity = 0.52). After unidirectional poling, macroscopically aligned samples with pure crystals are achieved, which show a high spontaneous polarization (P-s) of 140 mC/m(2). Given the theoretical limit of P-s,P-beta=188 mC/m(2) for the neat beta crystal, the high P-s cannot be explained by the crystalline-amorphous two-phase model (i.e., P-s,P-beta=270 mC/m(2)). Instead, we deduce that a significant amount (at least 0.25) of an oriented amorphous fraction (OAF) must be present between these two phases. Experimental data suggest that the mobile OAF resulted in the negative and high d(33) for the poled BOPVDF. The plausibility of this conclusion is supported by molecular dynamics simulations. Piezoelectric polymers usually have rather low piezoelectric coefficients less than 30 pC/N. Here, the authors achieve a highly piezoelectric polymer (d(33)=-62 pC/N) based on a poled biaxially oriented poly(vinylidene fluoride) with a pure beta phase due to the mobile oriented amorphous fraction.

Automated summary

Researchers have successfully prepared a highly piezoelectric polymer with a higher piezoelectric coefficient than existing piezoelectric polymers, based on poled biaxially oriented poly(vinylidene fluoride) with a pure beta phase formed by orientation.