Development of pyroelectric ceramics for high-temperature applications

Ceramics based on Bi3NbTiO9 (BNT) were investigated for their high-temperature pyroelectric properties. Doping BNT with 0.05 atoms of WG+ donor ions decreased its DC conductivity, enhanced its dielectric strength and remnant polarization. Thick films of BNT produced by airflow deposition show preferential grain orientation and enhanced sinterability, giving improved polarizability and higher dielectric strength than the comparable ceramic. Further improvements in grain orientation and enhanced remnant polarization are derived by sintering under an applied electric field. Airflow deposition was also used to prepare graded films of Ba(1-x)SrxTiO3 (BST), showing temperature dependent hysteresis offsets that originate from asymmetric leakage currents and are not related to the pyroelectric properties. These graded films show an enhanced conventional pyroelectric coefficient over a wide temperature range. These results predict that a graded structure of BaBi2Ta2O9 and Bi3NbTi0.95W0.05O9 should show enhanced high-temperature pyroelectric properties.