Ultrahigh electrostrictive effect in potassium sodium niobate-based lead-free ceramics

Abstract The longitudinal electrostrictive coefficient Q33 for perovskite-structured ferroelectric ceramics is usually between 0.01-0.04 m4/C2. However, an ultra-low Q33 of only 0.0047 m4/C2 was identified in the 0.9K0.5Na0.5NbO3-0.1SrTiO3 (KNN-ST) composition. Despite the fact that superior piezoelectricity has been observed in KNN-based ceramics, this value is obviously much smaller than the normal value, according to the general cognition and the thermodynamic relationship between piezoelectric coefficient d33 and Q33. Therefore, we synthesized (1−x)(K0.45Na0.49Li0.06)NbO3-xSrTiO3 (KNLN-ST) and studied phase structure, dielectric and ferroelectric properties systematically. Our findings show that the Q33 in the KNLN-ST system (0.012-0.027 m4/C2) is within the reasonable range for perovskite-structured ferroelectric ceramics. Furthermore, an ultra-high electrostrictive strain (>0.3%) with ultra-low hysteresis was achieved in the 0.8KNLN-0.2ST sample. This research not only clarifies the electrostrictive effect in KNN-based systems, but it also broadens the potential application field of KNN-based ceramics to electrostrictive actuators.