A pyroelectric phenomenon is a manifestation of the temperature dependence of spontaneous polarization on certain solids, which can be either single-crystal or poly-crystalline aggregates. When the temperature of the material is slightly increased, the electrical polarization of the material changes, and voltage can be measured between certain faces of the pyroelectric sample. Conversely, if the temperature of the material is lowered by the same amount, the same magnitudes of polarization and voltage are found with the signs reversed. Thus, pyroelectric materials provide a means of producing infrared (IR) detectors that conveniently operate at room temperature. In this chapter, a number of fundamental aspects of pyroelectricity are described regarding its application in IR detection and energy harvesting. Pyroelectric materials form a subgroup of piezoelectrics, while ferroelectrics form a subgroup of pyroelectrics. Relationships between crystal structure and relevant properties are discussed along with important candidate materials and their applications.
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