ABSTRACT
Surface charges due to internal electric polarization of a material which has a definiteaxial crystal symmetry cannot be observed when the material is at thermal eqUilibrium with its surroundings, because stray charges are attracted and trapped on its surfaces and neutralize surface charges. However, if the temperature of the material is changed within a short time by an external source such as conduction of heat or incidence of radiation, its internal polarization will be changed and the resulting surface charges can be measured by an external electric circuit before they are neutralized by other stray charges. It is obvious that devices using this pyroelectric effect have the following characteristics: electrical response to rate of temperature change, capacitive element, response independent of wavelength of absorbed radiation, and cooling not required. Therefore an uncooled pyroelectric radiation detector using an element of high pyroelectric coefficient is very useful for detection of weak incident radiation. At present the main practical use of pyroelectric devices is in various applications of incident radiation detection.
