Flexible PbTiO3-nanowires/ P(VDF-TrFE) composite films and their dielectric, ferroelectric and pyroelectric properties

Flexible composite films with PbTiO3 monocrystalline nanowires as fillers and poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) as matrix were prepared by solution-casting and subsequent hot-pressing process. It was found that hot-pressing step is necessary to eliminate the small portion of γ-phase in the solution-cast P(VDF-TrFE) film which could strongly suppress the switchability of the P(VDF-TrFE) matrix. Dielectric, ferroelectric and pyroelectric properties of the nanocomposites have been systematically studied by varying mass fraction of the nanowire fillers from 0 wt% to 50 wt%. Enhanced dielectric permittivities were obtained by incorporating PbTiO3 nanowires without sacrificing the dielectric loss properties. The relative permittivity and dielectric loss of the composites were greatly decreased after poling. P-E loops characteristic of ferroelectrics were observed in all the two-step processed films, showing a highest Pr of about 6.21 μC/cm2 at 30 wt% loading content. Pyroelectric coefficient p of the composites increases with the mass fraction of PbTiO3 nanowires as well as with the temperature, with a value of 52.7 μC/(m2 K) for pure P(VDF-TrFE) film at 45 °C and 72.8 μC/(m2 K) for 50 wt% PT/P(VDF-TrFE) composite film at 45 °C. The voltage FOM (FV) decreases as the loading of PbTiO3 nanowires increases (more prominently after 10 wt%), while detectivity FOM (FD) keeps a relatively high value on the same level (between 18 × 10−6 Pa−1/2–20 × 10−6 Pa−1/2) for 0–30 wt% loading content.