Ferroelectric switching characteristics of 73/27 copolymer of vinylidene fluoride and trifluoroethylene

Abstract

Abstract Ferroelectric polarization‐reversal switching of vinylidene fluoride—trifluoroethylene copolymer with 73 mol % of vinylidene fluoride is investigated under a variety of conditions in an attempt to derive detailed information on the polarization reversal of the polymer. The electric‐field dependence of switching time t s obeys an exponential law. The temporal change of switching current density J is presented in the form J /( P s − P ) versus time ( P is the polarization, and P s is its saturation value), which is free of the depolarization‐field effect and discriminates in a straightforward manner between acceleration and deceleration of switching. Effects of the annealing of samples upon t s are observed together with changes in the degree of crystallinity. Effects of space charge distribution upon t s are investigated by applying two successive pulses, positive and negative, with varied intervals t w between the two. The dynamics of space charge redistribution is elucidated from the t w dependence of the t s of the second pulse. The temperature dependence of t s indicates that the switching becomes critically fast as the phase‐transition temperature is approached.