Polymers, Piezoelectric

Abstract Piezoelectric polymers have been known for more than forty years, but in recent years they have gained repute as a valuable class of “smart materials.” The most popular smart materials are piezoelectric materials, magnetostrictive materials, shape‐memory alloys, electrorheological fluids, electrostrictive materials, and optical fibers. Magnetostrictives, electrostrictives, shape‐memory alloys, and electrorheological fluids are used as actuators; optical fibers are used primarily as sensors. Among these active materials, piezoelectric materials are most widely used because of their wide bandwidth, fast electromechanical response, relatively low power requirements, and high generative forces. Piezoelectricity is a property of many noncentrosymmetric ceramics, polymers, and other biological systems. Pyroelectricity is a subset of piezoelectricity, whereby the polarization is a function of temperature. Some pyroelectric materials are ferroelectric, although not all ferroelectrics are pyroelectric. Ferroelectricity is a property of certain dielectrics that exhibit spontaneous electric polarization that can be reversed in direction by applying an appropriate electric field. Traditionally, ferroelectricity is defined for crystalline materials, or at least in the crystalline region of semicrystalline materials. In the last couple of years, however, a number of researchers have explored the possibility of ferroelectricity in amorphous polymers, that is, ferroelectricity without a crystal lattice structure.