Temperature Effect on Ferroelectric Polarization Switching in Poly(vinylidene fluoride)

Abstract

Ferroelectric polarization switching experiments were carried out on Form I crystal of poly(vinylidene fluoride) over a temperature range from −76°C to 125°C and at applied electric fields E up to 200 MV m1. At 25°C, notable polarization switching currents which decayed within a few ms were observed at E≥75 MV m−1. These currents became more intensive with increasing applied electric field. The maximum switching current density Jmax and the maximum switching time τmax could be expressed approximately by Jmax (Am−2)=0.72 (E−75) and τmax−1 (s−1)=37(E−75), respectively, as also in the case with common ferroelectric crystals such as BaTiO3 and Rochelle salts. The polarization switching behavior changed remarkably with temperature and could be separated into three parts at about −44°C and 60°C. These temperatures coincide well with the reported β (glass transition) and α (crystalline) relaxation temperatures, respectively. This fact indicates that the polarization switching phenomenon in poly(vinylidene fluoride) has close correlation with molecular chain motions. Finally, molecular motions responsible for the polarization switching in the three temperature regions are discussed.