Dielectric and pyroelectric properties of (Ba,Sr,Ca)TiO3 ceramics for uncooled infrared detectors

(Ba0.6Sr0.3Ca0.1)TiO3 (BSCT) powders, which were prepared by the sol-gel method using a solution of Ba, Sr and Ca acetate and Ti isopropoxide, were spray-dried under the optimum conditions of a 10000 rpm atomizer speed and 1.5 wt% polyvinyl alcohol (PVA) addition. BSCT ceramics, undoped and doped with MnCO3 (0.1 mol%) and Y2O3 (0-0.9 mol%), were fabricated by the cold isostatic press method; and then the structural and electrical properties as a function of the Y2O3-dopant amount were studied. The specimen, doped with more than 0.5 mol% Y2O3, showed small and uniform grains of 1-3 mu m in diameter. The Curie temperature and the maximum dielectric constant decreased with increasing Y2O3 content and the dielectric loss of the specimen, doped with 0.5 mol% Y2O3, showed a minimum value of 0.009 at the Curie temperature. The pyroelectric coefficient decreased as the dopant of Y2O3 increased and the doped specimen of 0.3 mol% Y2O3 showed a good value of 354 x 10(-9) C/cm(2)K under a 4kV/cm DC bias field. The figure of merit F.M.D* for specific detectivity (D*) of the specimen, doped with 0.5 mol% Y2O3, showed the highest value of 8.9 x 10(-9) Ccm/J.