Hard Piezoelectric Properties of MnCO-Doped Lead-Free BiFeO-BaTiO Ceramics with High Curie Temperature.

Lead-free BiFeO-BaTiO (BF-BT) ceramics show high potential for piezoelectric sensors, actuators, and high-power transducers owing to their excellent piezoelectric properties and high Curie temperatures (). Hard piezoelectric material used in high-power transducer applications must exhibit a high mechanical quality factor (), high coercive field (), high , and low dielectric loss (tan δ). Herein, the effects of doping in BF-BT ceramics with the hard acceptor dopant Mn are investigated to enhance their hard piezoelectric properties. The 0.8Bi(FeMn)O-0.2BaTiO ( = 0, 0.005, 0.01, 0.015, and 0.02) ceramics are prepared using solid-state reaction and water-quenching processes. The increasing of the Mn content in BF-BT ceramics boosts the piezoelectric charge sensor coefficient (), , , planar piezoelectric coupling factor (), , and internal bias field (), reaching their maximum values at = 0.01 ( = 74 pC/N, = 757, = 652 °C, = 0.26, = 65 kV/cm, and = 6.2 kV/cm) with the lowest loss (tan δ = 0.009). Then, the hard piezoelectric properties deteriorate gradually with an increasing Mn content. The ferroelectric domain structure and dynamics are compared to defect-related ferroelectric and piezoelectric properties. These results show that the hard acceptor Mn in the BF-BT ceramics improves the performance of lead-free ceramics for high-power piezoelectric transducers in high-temperature environments.