Enhanced strain and electrostrictive properties in lead-free BNT-based ceramics via rare earth doping

Bi0.5Na0.5TiO3 (BNT)-based ceramics are one of the most promising lead-free ferroelectrics due to their high strain property. Compared to other chemical modifications, rare earth ions doping provides significant possibility to optimize the strain property of BNT-based ceramics. In this work, the effects of rare earth ions on phase structure, microstructure, and strain & electrostrictive properties of lead-free BNT-based ceramics were systematically investigated. Rare earth ions (i.e., La3+, Sm3+, Yb3+, Dy3+, and Nd3+) were selected as the doping ions. Introducing moderate La3+ ions can drive the ferroelectric state of BNT-based ceramics to nonergodic relaxor state or ergodic relaxor state. The enhanced strain response of ∼0.40–0.42% and high converse piezoelectric coefficient of ∼600–630 pm/V can be achieved under 60–70 kV/cm for La3+-doped ceramic with nonergodic relaxor state. Besides, the giant electrostrictive coefficient Q33 of ∼0.047 m4/C2 can be obtained for La3+-doped ceramic with ergodic relaxor state. Other rare earth ions also present the promotion effect on strain enhancement for BNT-based ceramics. This study affords a significant guidance to optimize strain and electrostrictive properties of BNT-based ceramics via rare earth ions doping.