Large electric field-induced strain in AgNbO3-modified 0.76Bi0.5Na0.5TiO3-0.24SrTiO3 lead-free piezoceramics

Bi0.5Na0.5TiO3-based lead-free piezoceramics with large strain output are of great importance in the application of piezoelectric actuators. AgNbO3-modified 0.76Bi0.5Na0.5TiO3-0.24SrTiO3 (BNT-24ST) lead-free piezoceramics were synthesized by conventional solid-state reaction method. The effects of AgNbO3 on the structures, dielectric, ferroelectric and piezoelectric properties were carefully investigated. A large electrostrain and normalized strain (d33* = Smax/Emax) of 0.27% and 700 pm/V, were obtained respectively at low electric field (40 kV/cm) for 1 mol.% AgNbO3-doped BNT-24ST. AgNbO3 doping modified the phase composition which contained moderate amounts of tetragonal and rhombohedral phase by shifting its TF-R to below room temperature. Moreover, the reversible field-induced phase transition between relaxor and ferroelectric made contributions to its large strain related properties. This work has confirmed that the actuating performance of BNT-ST-based piezoceramics can be further improved by an easy and cost-effective composition engineering method and showed it a promising candidate for lead-free actuator material.