Improved Dielectric Tunability in Stretched P(VDF-DB)

Dielectric tunable materials have been widely used as various microwave devices, including varactors, phase shifters, and tunable resonators. Ferroelectric fluoropolymers show great potential in microwave tunable devices owing to their outstanding dielectric properties. However, the dielectric tunability of fluoropolymers was rarely reported due to their low dielectric constant compared to ferroelectric ceramics. Herein, the effects of chemical structure and orientation on the conformation, crystal form, dielectric performances, and dielectric tunability of poly(vinylidene fluoride) bearing inner CF = CH double bond [P(VDF-DB)] were investigated. The resultant relaxor ferroelectric (RFE) copolymer exhibits large dielectric constant and tunability as a result of its phase transition temperature close to room temperature. A tunability of up to 73% was achieved in this stretched P(VDF-DB) at room temperature when a dc electric field of 100 MV/m was applied.