1 - Introduction to ferroelectrics and related materials

Abstract

Ferroelectrics are the materials with switchable spontaneous polarization. Switching of polarization from one state to another by the application of an electric field gives rise to a hysteresis loop, the signature of ferroelectricity. In different modes of operation, ferroelectrics can be used to harvest energy from distinguished sources such as solar, thermal, magnetic, wind, and mechanical vibrations. Present chapter reviews the fundamental aspects of ferroelectricity and the other related phenomena utilized in different modes of energy harvesting. The stability of more than one polarization states in ferroelectrics has been discussed in terms of its thermodynamic formulation. Absence of the center of symmetry is the necessary condition for an insulating material to be ferroelectric. On the basis of their chemical nature and formula unit, ferroelectrics are divided into several broad categories. From the application point of view, perovskites are the most interesting class of ferroelectrics with superior functional behavior, ease of the synthesis, and conducive operational range of temperature. Distortion of the unit cell from ideal cubic symmetry and domain structure, the two most important aspects of perovskites in determining their functional behavior, have been discussed. Piezoelectricity and pyroelectricity, the two phenomena closely related to ferroelectricity and utilized in different aspects of energy harvesting, have been discussed as well. Since all these properties are tensorial in nature, a brief account has been provided reviewing the effect of crystallographic nature of materials on their functional anisotropy. In the end, different characterization techniques used to characterize ferroelectric and related materials have been introduced, followed by a brief account on the application of these materials in different models of energy harvesting.