Large electrostrictive response in W-Mg co-doped Na0.5Bi0.5TiO3-based ceramics via defect complex designing

Lead-free electrostrictors based on bismuth sodium titanate (Bi_0.5Na_0.5TiO₃, BNT) are critical for sustainable actuator technologies, yet their performance limitations necessitate innovative defect engineering strategies. Here, we report a synergistic B-site donor-acceptor co-doping approach to amplify the electrostrictive response via tailored defect complex. By incorporating W^{6 +}-Mg²⁺ co-doping, which results in electrostatic field, stress field and electronegativity difference, the domain switching is promoted and the B-site ions are limited. On this basis, we demonstrate the electrostrictive coefficient of 0.0543 m⁴/C² at 0.1 Hz and stable around ∼0.037 m⁴/C² at 100 Hz. This work establishes a universal co-doping paradigm to optimize lead-free electrostrictors, bridging atomic-scale defect control to macroscopic electromechanical performance.