Effect of Electric Field on the Phase Transition in Vinylidene Fluoride-Trifluoroethylene Copolymers

The pyroelectric constant of poled VDF/TrFE copolymers during heating shows a peak associated with a ferroelectric phase transition. When the bias electric field is applied in the same direction as the remanent polarization, the peak shifts to a higher temperature. When the bias electric field is applied in the reverse direction, the peak shifts to a lower temperature, followed by reversal of the sign of the pyroelectric constant, and a second peak. The shift of peak temperature with bias field is discussed on the basis of the Clausius-Clapeyron equation. A possibility is suggested to make a memory element utilizing thermal polarization reversal and pyroelectric detection.