High strain in lead-free Nb-doped Bi 1/2 (Na 0.84 K 0.16 ) 1/2 TiO 3 –SrTiO 3 incipient piezoelectric ceramics

Lead-free 0.96[Bi 1/2 (Na 0.84 K 0.16 ) 1/2 (Ti (1− x ) Nb x )O 3 ]–0.04SrTiO 3 (BNKTN–ST, with x = 0–0.030) ceramics were synthesized by a conventional solid-state reaction technique. Polarization and strain hysteresis loops indicated a significant disruption of ferroelectric order accompanied by an enhanced field-induced strain ( S = 0.438%) with a high normalized strain S max / E max of 876 pm/V at 5 kV/mm. Their reproducibility was confirmed by the fabrication of a 10-layered stack-type multilayer actuator, which demonstrated a normalized strain S max / E max of 720 pm/V.