High Energy Storage Density and Large Strain in Bi(Zn_2/3Nb_1/3)O₃‑Doped BiFeO₃–BaTiO₃ Ceramics

High recoverable energy density (<i>W</i>_rec ∼ 2.1 J/cm³) was obtained in (0.7 – <i>x</i>)­BiFeO₃-0.3BaTiO₃-<i>x</i>Bi­(Zn_2/3­Nb_1/3)­O₃ + 0.1 wt % Mn₂O₃ (BF-BT-<i>x</i>BZN, <i>x</i> = 0.05) lead-free ceramics at <200 kV/cm. Fast discharge speeds (<0.5 μs), low leakage (∼10^–7 A/cm²), and small temperature variation in <i>W</i>_rec (∼25% from 23 to 150 °C) confirmed the potential for these BiFeO₃-based compositions for use in high energy density capacitors. A core–shell microstructure composed of a BiFeO₃-rich core and BaTiO₃-rich shell was observed by scanning and transmission electron microscopy which may contribute to the high value of energy density. In addition, for <i>x</i> = 0.005, a large electromechanical strain was observed with <i>S</i>_pos = 0.463% and effective <i>d</i>₃₃* ∼ 424 pm/V, suggesting that this family of ceramics may also have potential for high strain actuators