Electrostrictive Phenomena Associated with Polarization Reversal in Ferroelectric Polymers

The electrostriction effect of ferroelectric vinylidene fluoride (VDF) and trifluoroethylene copolymers was studied by measuring their dimensional variation under an external electric field changing beyond a coercive electric field. The relationship between strain and polarization for the copolymer which includes a 54 mol% VDF reveals a parabolic electrostriction relationship over the entire measurement range of the strain-polarization relationship. The relationship for the copolymer which includes a 73 mol% VDF, however, deviates from the parabolic relationship. The result is discussed in terms of the thermodynamics of a ferroelectric phase transition. Furthermore, the origin of the ferroelectricity of these copolymers is discussed.