Ferroelectricity in VF₂based copolymers

Abstract

Abstract Introduction of monomers of tri-fluoro or tetra-fluoro-éthylene (F3E or F4E) along the chain of polyvinylidene fluoride (PVF2 is able to induce spontaneous crystallization in a ferroelectric structure. Such copolymers exhibit a ferroelectric transition to a disordered para-electric phase. After a short review concerning the phase diagrams and the piezo and pyroelectric properties, we present recent results on the ferroelectric behaviour of VF2-F3E copolymers and on their first order ferroelectric transition. This investigation is based on dielectric measurements, second harmonic generation of light, × ray diffraction, thermal expansion measurements and Brillouin spectroscopy. Interpretation emphasizes the composite structure of these semi crystalline materials.