Abstract:
Pyroelectric infra-red detector arrays provide an attractive solution to the
problem of collecting spatial information in the far IR. They are only sensitive
to changes in the IR flux and are well suited to sensing movements of people.
The applications of low cost arrays with limited ( a few hundred) elements for
people sensing and radiometry will be illustrated. The performances of uncooled
pyroelectric arrays are ultimately driven by the materials used. For this
reason, continuous improvements in materials technology and figures-of-merit
(FoM) are important. The performance of dense, bulk pyroelectric ceramics has
not increased for several years, but nevertheless it is possible to obtain
significant improvements in performance through the use of tape-cast,
functionally gradient materials (FGMs) in which controlled porosity is used to
control the permittivity and heat capacity of the material. A model for the
performance of such a material will be presented, and compared with
experimentally determined properties of FGMs based on a modified-PZT
pyroelectric ceramic. The use of ferroelectric thin films is offering
considerable potential for low cost and high performance. It will be shown that
the introduction of controlled amounts of porosity can have a significant
positive effect on the relevant pyroelectric FoM.
