High performance Aurivillius-type bismuth titanate niobate (Bi3TiNbO9) piezoelectric ceramics for high temperature applications
This paper reports the significant improved piezoelectric properties of high temperature bismuth titanate niobate (Bi3TiNbO9, BTN) polycrystalline ceramics. The piezoelectric performance of BTN ceramics is significantly enhanced by cerium modifications. The dielectric measurements indicate that the Curie temperature Tc gradually decreases over the temperature range of 907-889 °C with cerium contents increasing up to 0.7 wt%. The BTN-5Ce (BTN+0.5 wt% CeO2) exhibits optimized piezoelectric properties with a piezoelectric constant d33 of 16 pC/N, which is five times the value of unmodified BTN (d33~3 pC/N), while BTN-5Ce maintains a high Curie temperature Tc of 894 °C. The temperature-dependent electrical impedance and electromechanical coupling factors (kp, and kt) reveal that the BTN-5Ce exhibits thermally stable electromechanical coupling characteristics up to 500 °C but significantly deteriorates at 600 °C due to high conductivity at a higher temperature. The thermally stable electromechanical properties in combination with the ceramics׳ high electrical resistivity (106 Ω cm at 500 °C) and high Curie temperature (~900 °C) demonstrate that cerium-modified BTN ceramics are good materials for high temperature sensing applications.