Computer simulation of switching processes in polyvinylidene fluoride and its copolymers

Abstract

Abstract Ferroelectric switching transients P vs. t of polyvinylidene fluoride (PVDF) and its copolymer with trifluoroethylene (TrFE) are simulated by computer calculations on the basis of a nucleation and growth mechanism. The effect of the growth dimension, types of rotations, 180° or 60°, and domain size are examined. The shape of the derivative ∂P/∂logt expressed in terms of its half-width ΔW depends strongly upon the ratio of the growth velocity v to the nucleation probability p. When v/p ≪ 1, ΔW is 1 decade (sigle relaxation process) because the nucleation dominates. When v/p ≫ 1, it is also 1 decade because of limited domain size. At intermediate v/p ratios, ΔW is ½-½ depending upon the growth dimension. The 180° and 60° models do not result in notable differences in ΔW values except for a trailing in the latter. The switching transients observed in PVDF can be fitted by either one or two dimensional model. A very sharp ∂P/∂logt peak with ΔW = ⅕ observed in the VDF/TrFE copolymer requires a coopera...