Dielectric and Pyroelectric Properties of (Ba,Sr,Ca)TiO₃ Ceramics for Uncooled Infrared Detectors

(Ba_0.6Sr_0.3Ca_0.1)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.