High-piezoelectric lead-free BiFeO3 -BaTiO3 ceramics with enhanced temperature stability and mechanical properties

BiFeO3BaTiO3 (BF-BT) ceramics exhibit higher piezoelectric coefficients (d(33)), Curie temperatures (T-C), and temperature stability than other high-temperature lead-free piezoelectric materials. However, despite their crucial role in piezoelectric devices, the mechanical properties of BF-BT ceramics have been underexplored. A thorough evaluation of the mechanical properties of BF-BT is crucial for developing cost-effective and durable lead-free piezoelectric ceramics. Moreover, the specific causes of the high piezoelectric response and excellent temperature stability of BF-BT ceramics remain unclear owing to the instrumental detection threshold, which limits experimental studies to temperatures above 140 degrees C and below the degradation temperature of d(33). To investigate the intrinsic origins of the high piezoelectricity and temperature stability of BF-xBT ceramics and to enhance their mechanical properties, a two-step sintering process is used to fabricate these ceramics (0.25 <= x <= 0.40). Owing to improvements in grain refinement and reduced Bi3+ volatilization, the BF-0.33 BT ceramic exhibits enhanced overall performance, with a modified small punch strength of 155 MPa, Vickers hardness of 5.2 GPa, a d(33) of 220 pC/N at room temperature, T-C of 466 degrees C, and d(33) values exceeding 400 pC/N at 260 degrees C. Phase-field simulations, which address the limitations of device detection thresholds, reveal that with increasing temperature, the domain structure relaxes, and polarization intensity decreases. This indicates that changes in the high-temperature piezoelectric properties can be attributed to domain structure relaxation and the increase in dielectric constant. Overall, BF-BT ceramics exhibit superior piezoelectric performance, mechanical properties, and temperature stability, making them highly suitable for use in high-temperature and demanding environments. (c) 2024 The Authors. Published by Elsevier B.V. on behalf of The Chinese Ceramic Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).