High Energy Storage Density and Large Strain in Bi(Zn2/3Nb1/3)O₃-Doped BiFeO₃–BaTiO₃ Ceramics

High recoverable energy density (Wrec ∼ 2.1 J/cm3) was obtained in (0.7 – x)BiFeO3-0.3BaTiO3-xBi(Zn2/3Nb1/3)O3 + 0.1 wt % Mn2O3 (BF-BT-xBZN, x = 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 Wrec (∼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 x = 0.005, a large electromechanical strain was observed with Spos = 0.463% and effective d33* ∼ 424 pm/V, suggesting that this family of ceramics may also have potential for high strain actuators.