Piezoelectric properties and thermal stabilities of strontium bismuth titanate (SrBi4Ti4O15)

Bismuth layer-structured ferroelectric (BLSF) compound strontium bismuth titanate (SrBi4Ti4O15, SBT) with cerium modifications have been synthesized using conventional solid-state processing. X-ray powder diffraction (XRPD) analyses reveal that the cerium-modified SBT ceramics have a pure four-layer Aurivillius-type structure. The dielectric, ferroelectric, and piezoelectric properties of the cerium-modified SBT ceramics are investigated in detail. The results indicate that the cerium modifications into SBT increase the densities, decrease the sintering temperature, lower the dielectric loss tanδ, and reduce the coercive filed Ec. The piezoelectric measurements show that cerium is very effective in promoting the piezoelectric properties of SBT ceramics. The SBT ceramics modified with 4 mol% CeO2 (SBT-4Ce) exhibit the optimized piezoelectric properties, with a piezoelectric constant d33 of 27 pC/N, which is the highest value among the modified SBT-based piezoelectric ceramics ever reported. The temperature-dependent electrical impedance and electromechanical coupling coefficients (kp and kt) reveal that the electromechanical coupling characteristics have a significant deterioration at ~400 °C because of the high conductivity at high temperature. But the temperature-dependent frequency constants (Np and Nt) and thermal annealing analyses indicate the cerium-modified SBT ceramics have good thermal stabilities of piezoelectric properties up to 450 °C. These results demonstrate that the cerium-modified SBT ceramics are promising materials for high temperature piezoelectric sensors applications.