Origin and magnitude of the large piezoelectric response in the lead-free (1-x)BiFeO3-xBaTiO3 solid solution

Mechanisms and magnitudes of the large piezoelectric response observed in lead-free (1-x) BiFeO3-xBaTiO3 (BFBT) ceramics are investigated. Preceding studies reported significant strain hysteresis and hard ferroelectric behavior in BFBT leading to a small low-field piezoelectric coefficient, instability of the poled domain state, and rapid degradation of piezoelectric properties. The current investigation shows that under application of a suitable direct current (dc) bias to stabilize the ferroelectric phase low- and high-field piezoelectric coefficients (d33) of 150 pC/N and 250 pC/N are observed for the composition 0.67BiFeO3-0.33BaTiO3 + 0.1 wt% MnO with a Curie temperature of 605 °C. Such enhancement of electromechanical properties under dc bias is in contrast to the expected behavior in traditional piezoelectric materials such as soft lead zirconate titanate (PZT). The large piezoelectric coefficients confirm strong intrinsic and extrinsic contributions to the piezoelectric response in BFBT, which coupled with high ferroelectric Curie temperature TC > 500 °C, suggests BFBT-based materials as promising lead-free alternatives to PZT piezoceramics.