Pyroelectric infra-red detector arrays provide an attractive solution to theproblem of collecting spatial information in the far IR. They are only sensitiveto 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 forpeople sensing and radiometry will be illustrated. The performances of uncooledpyroelectric arrays are ultimately driven by the materials used. For thisreason, continuous improvements in materials technology and figures-of-merit(FoM) are important. The performance of dense, bulk pyroelectric ceramics hasnot increased for several years, but nevertheless it is possible to obtainsignificant improvements in performance through the use of tape-cast,functionally gradient materials (FGMs) in which controlled porosity is used tocontrol the permittivity and heat capacity of the material. A model for theperformance of such a material will be presented, and compared withexperimentally determined properties of FGMs based on a modified-PZTpyroelectric ceramic. The use of ferroelectric thin films is offeringconsiderable potential for low cost and high performance. It will be shown thatthe introduction of controlled amounts of porosity can have a significantpositive effect on the relevant pyroelectric FoM.
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