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 µm 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 ×10-9 C/cm2K under a 4 kV/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 ×10-9 Ccm/J.