Piezoelectricity in β-phase poly(vinylidene fluoride) having a ’’single-crystal’’ orientation

Abstract

β‐phase PVF₂ films having a ’’single‐crystal’’ orientation (single‐crystal analog) were prepared by a combination of drawing, rolling, and annealing, applied in sequence. X‐ray diffraction patterns revealed that the polar b axis was preferentially oriented normal to the surface of the film while the a and c axes were in the plane of the film, lying along two mutually orthogonal axes. Piezoelectric outputs (d₁₃) of the films were compared with those of drawn‐only films under the same poling conditions (about 500 kV/cm) and found to be on average about 25% higher than the latter. X‐ray and dynamic mechanical data showed that the improvement depends primarily on the preferred alignment of the a and b axes in the plane normal to the draw and rolling direction.