Studies on doped triglycine sulphate (TGS) for pyroelectric detector applications

Abstract

It is now an established fact that the infrared detectors based on pyroelectric materials offer the advantage of room temperature operation and wide spectral response. A survey of a number of possible materials for use in pyroelectric detectors shows that TGS and its derivatives are most promising. The major disadvantage of TGS is its tendency to depole near curie temperature. Attempts have been made to increase the curie temperature. Attempts have been made to increase the curie temperature and check the depoling by doping TGS with L-alanine. This results in a biased hysteresis and better pyroelectric performance. But these crystals generally crack during the process of target preparation for use in IR detector applications. However, doping with inorganic ions makes the crystal lattice rigid with no improvement in pyroelectric properties. It was, therefore, considered interesting to make an extensive study of doped TGS crystals that may lead to better operating characteristics to TGS or L-alanine doped TGS (LLATGS). The dopants studied were amino acids, inorganic ions ⁺L-alanine and dipolar organic impurities having NH₂ group. The properties investigated were pyroelectric coeffiecient, dielectric constant, ferroelectric transition temperature, and self-bias fields. Using these properties applicable pyroelectric figures of merit are calculated for comparison. It has been found that these crystals can be good target element and possess good mechanical properties for ease of target preparation. The merits and demerits of using these crystals are also discussed.