Enhanced recoverable energy density of 0.94Bi_0.50(Na_0.78K_0.22)_0.50Ti_1−x(Fe_0.50Nb_0.50)_xO₃–0.06BaZrO₃ lead-free relaxor ceramics doped by (Fe_0.50Nb_0.50)⁴⁺ complex ions

The innovative 0.94Bi_0.50(Na_0.78K_0.22)_0.50Ti_1−x(Fe_0.50Nb_0.50)_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 (Fe_0.50Nb_0.50)⁴⁺ complex ions had completely dissolved in the lattice and constructed a single solid-solution. The addition of (Fe_0.50Nb_0.50)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 (Fe_0.50Nb_0.50)⁴⁺ complex ions. The highest recoverable energy density (W_rec) ~ 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.