Pyroelectric ceramics and devices for thermal infrared detection and imaging

Pyroelectric detectors offer major advantages in terms of cost and ease-of-operation over cooled photon detectors of long wavelength infrared radiation. This paper reviews the requirements of a pyroelectric material to maximise its effectiveness in different types of detector and compares the properties of ferroelectric ceramics with those of different single crystal materials. The control of the electrical properties of modified lead zirconate by doping is discussed. The concept of using a ferroelectric close to Tc under an applied electric bias as a dielectric bolometer is introduced and the properties of three different ferroelectric ceramics, barium strontium titanate, lanthanum-doped lead magnesium niobate and lead scandium tantalate are compared. It is shown that figures-of-merit can be achieved in lead scandium tantalate under DC bias which are up to three times greater than more conventional pyroelectric materials. Finally, the use of pyroelectric ceramics is illustrated by reference to selected devices for thermal imaging applications.