ABSTRACT
Classication of dielectric materials into different classes as piezoelectric, pyroelectric, and ferroelectric is described in Chapter 1. This is brie¤y repeated here for clarity and relevance. Piezoelectric materials are a special class of dielectric materials that exhibit transducer characteristics by virtue of their noncentrosymmetric crystal structure. Some piezoelectric materials possess spontaneous polarization that decreases with increasing temperature, and these are classied as pyroelectric materials. In some of these pyroelectric materials, the spontaneous polarization can be reoriented by applying an external electric eld, and such materials are classied as ferroelectric materials. Thus, ferroelectric materials possess both pyroelectric and piezoelectric characteristics.
