Dielectric, ferroelectric, and energy conversion properties of a KNN/P(VDF-TrFE) composite film

An environmentally friendly ceramic K 0.5 Na 0.5 NbO 3 is synthesized using traditional solid-state reaction process, and followed that a group of flexible K 0.5 Na 0.5 NbO 3 /poly(vinylidene fluoride-trifluoroethylene) (KNN/P(VDF-TrFE)) piezoelectric composite films are prepared by a conventional solution casting method. We find 3%-25% doping of KNN in mass ration (wt%) can fabricate the dielectric and ferroelectric properties of the KNN/P(VDF-TrFE) films, and a proper content of 15 wt% of KNN favors of the piezoelectric phase of P(VDF-TrFE) and thereby contributes to the piezoelectric performance of these composite films, effectively. As such, a maximum dielectric constant ( ε r ) of 20.5 and a large residual polarization ( P r ) of 13.6 μC/cm 2 are obtained in KNN/P(VDF-TrFE) composite film, respectively. Attractively, this composite film exhibits a high-piezoelectric coefficient ( d 33 ) of -24 pC/N, and consequently is beneficial to a large output voltage of 3.2 V for pulse stress testing, which provides a referenced material for the prospect of application in energy conversion area.