Enhanced Piezoelectric and Acoustic Performances of Poly(vinylidene fluoride-trifluoroethylene) Films for Hydroacoustic Application
Both scholars and engineers concerning flexible piezoelectric devices propose that poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) shows more merits than oriented polyvinylidene fluoride (OPVDF) in dielectric, piezoelectric, mechanic-electric, acoustic emission reception performance, etc. Thus, to clarify the differences between two sorts of polymers on their ferroelectric and piezoelectric behaviors, we systemically investigate their molecular structures and phase structures, and compare their dielectric properties and acoustic emission reception performance. We find that, for the wedge effect of TrFE, P(VDF-TrFE) possesses higher regular β phase crystal grains, which are easier to be ordered along the electric field and possess more ordered static charge distribution than that of OPVDF. Consequently, a considerable statured electric polarization (Pm~15 μC/cm2 under 225 MV/m), a large piezoelectric coefficient (d33~-22 pC/N) and a low coercive electric field (Ec~50 MV/m) are obtained in P(VDF-TrFE) films. It is worth noted that P(VDF-TrFE) shows a more stable d33 piezoelectric response (till 120oC) than that of the OPVDF. Additionally, P(VDF-TrFE) piezoelectric film exhibits a sensitive acoustic emission reception property approximate 70 dB, and an extensive response frequency range from 10 to100 kHz. Those properties combinatorically demonstrate that P(VDF-TrFE) piezoelectric film is a promising material for flexible and easy shaped electronic devices, including hydroacoustic sensors, actuators, and energy transfer units.