Enhanced recoverable energy density of 0.94Bi0.50(Na0.78K0.22)0.50Ti1−x(Fe0.50Nb0.50)xO3–0.06BaZrO3 lead-free relaxor ceramics doped by (Fe0.50Nb0.50)4+ complex ions

The innovative 0.94Bi0.50(Na0.78K0.22)0.50Ti1−x(Fe0.50Nb0.50)xO3–0.06BaZrO3 (BNKTBZ-xFN) lead-free relaxor ceramics were designed and fabricated by the conventional solid-state technique. The dielectric, ferroelectric, energy storage, and impedance performance of these ceramics were investigated systematically. XRD patterns revealed that the (Fe0.50Nb0.50)4+ complex ions had completely dissolved in the lattice and constructed a single solid-solution. The addition of (Fe0.50Nb0.50)4+ complex ions had an obvious impact on the grain size and crystallinity of BNKTBZ-xFN ceramics, which led to a large dielectric breakdown strength. In addition, the degree of diffusivity (γ) for BNKTBZ-xFN ceramics were increased from ~ 1.72 to ~ 1.93, indicating an enhanced relaxor behavior with the doping of (Fe0.50Nb0.50)4+ complex ions. The highest recoverable energy density (Wrec) ~ 1.20 J/cm3 and energy-storage efficiency (η) ~ 72% were attained at 120 kV/cm for BNKTBZ-2FN ceramic with the excellent fatigue resistance. Therefore, the BNKTBZ-2FN ceramic might be a promising candidate for energy-storage electronic devices.