Ferroelectric Behavior of Thin Films of Vinylidene Fluoride/Trifluoroethylene/Hexafluoropropylene Copolymer

Abstract

Ferroelectricity in vinylidene fluoride (VDF), trifluoroethylene (TrFE) and hexafluoropropylene (HFP) copolymers (P(VDF/TrFE/HFP)) with a low HFP content (lower than 11 mol%) has been investigated primarily through switching measurements using P(VDF/TrFE) as a comparison. Switching phenomena as a result of ultimately 180° rotations of individual molecular chains around their axes in crystalline regions were observed in P(VDF/TrFE/HFP) with an HFP content lower than 2.5 mol%. With increasing HFP content in P(VDF/TrFE/ HFP), the amount of reversed polarization decreases, and the dielectric permittivity at the Curie point becomes smaller. However, the switching times have very low dependence on the HFP content of P(VDF/TrFE/HFP). These results suggest that noncrystalline regions in P(VDF/TrFE/HFP) are similar to those in P(VDF/TrFE), and the disorder in crystalline regions of P(VDF/TrFE/HFP) increases compared to that in crystalline regions of P(VDF/TrFE).