Comparison of electrical response of beta PVDF and PVDF-TrFE sheets

Abstract

In this work, PVDF, indium tin oxide (ITO) coated 𝛽-PVDF and P(VDF-TrFE) free standing sheets have been studied in detail. Their structural, dielectric, and ferroelectric properties are compared. PVDF and P(VDF-TrFE) sheets are prepared by solvent casting technique. 𝛽-PVDF sheets were extracted from the etching of ITO by using Hydrochloric acid (HCl) as an etchant agent. The structural analysis of all the prepared samples is done using X-ray Diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). XRD and FTIR results show that P(VDF-TrFE) exhibits excellent crystallinity, followed by ITO etched PVDF and solvent casted PVDF. The higher crystallinity in P(VDF-TrFE) corresponds to steric hindrance between CHF and CH2. In dielectric spectrum of solvent cast PVDF and ITO etched PVDF, only glass transition process related with relaxation of polymer chains is observed and their dielectric constant are compareable. Important feature observed in dielectric spectrum of P(VDF-TrFE) is the phase transition from ferroelectric to paraelectric. The ferroelectric phase transition occurs at Tc=395 K. At Tc chain conformation changes from TTTT to TTTG. Ferroelectric measurements of this specimen further confirm this trend. Solvent casted PVDF exhibits lossy loops and indicates high leakage current. PVDF/ITO displays resistive loops bacause of lower electrical conductivity. ITO etched PVDF results in saturated loops due to coating of better electrode i.e. Ag. P(VDF-TrFE) emerges as well saturated loops, indicating excellent ferroelectric properties. The study further shows that removing ITO from PVDF through wet etching reveals the true electrical response. Additionally, adding TrFE to PVDF further enhance its ferroelectricity. The P(VDF-TrFE) sample exhibits a high dielectric constant and well-saturated 𝑃 − 𝐸 loops. This makes P(VDF-TrFE) an attractive candidate for energy storage devices due to its impressive dielectric properties. It can also be used as a piezoelectric device due to its substantial remanent polarization (Pr).