Study on the Polarization and Relaxation Processes of Ferroelectric Polymer Films Using the Sawyer-Tower Circuit with Square Voltage Waveform

Displacement-vs-electric field hysteresis (D-E) loops constructed on the Saywer-Tower circuit have been widely utilized to characterize the ferroelectric performance of ferroelectric materials. To overcome the disadvantages of the current Sawyer-Tower (ST) circuit in overestimated polarization from conduction loss and the disability in reflecting the polarization and relaxation processes, a ST circuit with square voltage waveform is developed for measuring the displacement of ferroelectric materials as a function of time under fixed electric field. By eliminating the conduction loss from the polarization and fitting the experimental results with the theoretical one, the characteristic parameters of a model ferroelectric material, poly(vinylidene fluoride-trifluoroethylene), have been obtained. The polarization and relaxation processes of the dipoles along the electric field have been finely illustrated for the first time, which cannot be given by the traditional ST possibly. Besides, more accurate parameters are obtained from the ST circuit with square voltage waveform than the traditional one to give an in-depth understanding of the energy storage and energy loss. This work might offer a robust method for the measurement of the polarization and relaxation processes in ferroelectric materials with desired accuracy.