Achieving superb electric energy storage in relaxor ferroelectric BiFeO3-BaTiO3-NaNbO3 ceramics via O2 atmosphere

Lead-free perovskite dielectric materials for storing electrical energy have been widely investigated due to their high polarization and reversible phase. However, their low electric resistivity limits the energy density and stability. In this study, the (1-x)(0.7BiFeO3-0.3BaTiO3)-xNaNbO3 ceramics (x = 0 – 0.2) were prepared using two sintering atmospheres (air and oxygen). A superb recoverable energy-stored density (Wrec) of 8.2 J/cm3 and efficiency (η) of 70% was achieved at x = 0.15 sintered in O2 atmosphere. The superior Wrec is due to the structural coexistence of ferroelectric rhombohedral (R3c), nonpolar cubic (Pm-3m), and antiferroelectric orthorhombic (Pbam) symmetries, tailored via antiferroelectric NaNbO3 addition. The improved breakdown strengths (up to 325 kV/cm) are due to the increased interatomic bonding linked to the BO6 octahedron and lattice network. Altogether, NaNbO3-substitution and O2 sintering synergistically resulted in excellent energy storage and pave a scheme of antiferroelectric-tailoring BiFeO3-BaTiO3–NaNbO3 relaxor ferroelectrics for dielectric capacitor.