It produces a lower intensity of radiation than the Nernst or Globar sources, but has a longer working life. In a pyroelectric material, when the field is removed, the polarisation persists. The degree of polarisation is temperature dependant. So, by sandwiching the pyroelectric material between two electrodes, a temperature dependant capacitor is made. The heating effect of incident IR radiation causes a change in the capacitance of the material.
Pyroelectric detectors have a fast response time.
They are used in most Fourier transform IR instruments. Photoelectric detectors such as the mercury cadmium telluride detector comprise a film of semiconducting material deposited on a glass surface, sealed in an evacuated envelope. Absorption of IR promotes nonconducting valence electrons to a higher, conducting, state. The electrical resistance of the semiconductor decreases. These are often double-beam recording instruments, employing diffraction gratings for dispersion of radiation.