Giant strains of 0.70% achieved via a field-induced multiple phase transition in BNT-based relaxor antiferroelectric ceramics

Bismuth sodium titanate (BNT)-based lead-free ceramics have attracted a great deal of attention due to their large electrostrains. In this work, a remarkably symmetric strain of 0.7% together with excellent temperature (0.5-0.7% from 25 to 100 degrees C)/frequency (Delta S<4% from 1 to 20 Hz) stability was observed in the 0.91(Bi0.5Na0.5) TiO3-0.06BaTiO3-0.03NaNbO3 (BNT-6BT-3NN) AFE P4bm ceramic through constructing R3c/P4mm/P4bm triple-phase coexistence phase boundary. Compared with other two compositions near double-phase coexistence ferroelectric (FE)-antiferroelectric (AFE) phase boundaries, the BNT-6BT-3NN ceramic exhibits a unique field-induced multiple phase transition from the initial AFE P4bm phase to the metastable FE P4mm phase and finally into the FE R3c phase. In-situ structural analysis evidenced a significantly enhanced lattice strain but a comparable strain value from domain switching in BNT-6BT-3NN compared with other compositions. The present study provides a novel strategy for designing high-performance large-strain ceramics in BNT-based relaxor AFE systems.