ABSTRACT
The pyroelectric effect in certain materials was recognized a long time ago, and such materials were referred as "electric stones." It was observed when such a stone was thrown in the fire, it started to generate electric charges and caused "cracking" sounds. This is basically due to the temperature dependence of the spontaneous polarization of a polar material. Practical applications of the pyroelectric effect in temperature sensors and IR light detectors have been enabling some commercial marketing of ferroelectric ceramics. A pyroelectric sensor is a device for transducing optical/thermal energy to electrical energy, and its sensitivity or figure of merit (FOM) can be evaluated in several ways. The converse effect of pyroelectricity is "electrocaloric effect." By applying the electric field on a pyrocrystal, we can expect a temperature rise/fall according to the polarity. The cooling function is of particular interest, aiming at the refrigeration application.
