Dielectric relaxation, impedance spectra, piezoelectric properties of (Ba, Ca)(Ti, Sn)O3 ceramics and their multilayer piezoelectric actuators

In this study, an improved method was developed for the preparation of lead-free (Ba1−xCax)(Ti0.91Sn0.09)O3 (BCTS) (0.02 ≤ x ≤ 0.07) ceramics by combining the conventional solid-state reaction with a gel precursor mixing method. The effects of Ca content on the microstructural, dielectric, impedance, piezoelectric and ferroelectric properties of the ceramics were systematically investigated. Dense ceramics with a uniform distribution of grain size and sharp grain boundaries were developed. Extremely high electrical properties of d33 ∼620 pC/N, kp ∼46% and ε ∼14500 were obtained at x = 0.03. A dielectric loss peak was observed, correlating to the oxygen vacancy relaxation at elevated temperature. Moreover, the dielectric properties vs. DC bias electric field and the temperature dependences of electrical properties were studied as well. Lastly, BCTS-based monolithic multilayer piezoelectric actuators were successfully fabricated showing large displacements under low driven voltages. These results would be valuable for understanding the electric properties of BCTS ceramics that would in turn extend their applications in multilayer piezoelectric devices.