Achieving ultrahigh electrostrain with giant piezoelectric strain coefficient in (Bi0.5Na0.5)TiO3-based ceramics via integrating NER/ER boundary and defect engineering

Ferroelectric ceramics with high electrostrain have been widely applied in actuators and sensors for their rapid response and precision. However, the current bottleneck is the inability to obtain superior electrostrain values along with high piezoelectric strain coefficient ( d 33 * ), limiting the practical applications. Herein, we report a remarkable enhancement of electrostrain values and d 33 * simultaneously in (Bi 0.5 Na 0.5 ) 0.93 Ba 0.07 Ti 1- x (Nb 0.5 Ga 0.5 ) x O 3 (BNBT- x NG, 0 ≤ x  ≤ 0.06) ceramics with the integration of nonergodic/ergodic relaxor (NER/ER) boundary and defect engineering at room temperature. This strategy by combining NER/ER boundary and defect engineering allow for highly asymmetric strain-electric field (S-E) loops with an ultrahigh and temperature-insensitive electrostrain of 0.73% as well as giant piezoelectric strain coefficient of 913 pm/V simultaneously. The electrostrain value is greater than most of the reported lead-free ceramics and even exceeds those of conventional lead-based materials. This work suggests an effective method for developing new lead-free ceramics to achieve high piezoelectric response.