Tailoring energy storage in Nb2O5-added 0.7BiFeO3–0.3BaTiO3 ceramics via A-site Gd3+ substitution

Perovskite BiFeO3-based capacitors have demonstrated potential for static electric energy storing applications with superb polarizations and rapid charge-discharge response. This report demonstrates a binary design with high storage energy densities using the lead-free 0.5 mol% Nb2O5–added 0.7(Bi1-xGdx)FeO3-0.3BaTiO3 ceramics (x = 0–0.40) tailored by the A-site gadolinium (Gd3+) substitution from ferroelectric to relaxor-ferroelectric state. An excellent recoverable energy density Wrec∼6.5 J/cm3 (at 260 kV/cm) and a storing efficiency η ∼75% (at 280 kV/cm) were respectively attained at x = 0.15 and x = 0.30. The breakdown electric field (Eb) rises from ∼120 to ∼260–280 kV/cm with increasing Gd3+ from x = 0 to x = 0.4 owing to the improved interatomic bonding, including the B-O bonds and the BO6 oxygen octahedron. The high recoverable energy densities can be correlated to the evolution of multi-phase lattice distortions, nanoscale domains, and polar nanoregions. This study signifies that the Gd3+-modified BF-BT ceramics can be candidates for electric energy-storing capacitors.