Enhancement of energy storage performance in lead-free barium titanate-based relaxor ferroelectrics through a synergistic two-step strategy design

Dielectric capacitors are widely used because of their advanced performance, including superior power density and high charge–discharge speed. Nevertheless, limitations in energy-storage density (W_rec), efficiency (η) and thermal stability hinder their practical application. Herein, these concerns are addressed using a synergistic two-step strategy of designing the composition of Bi(Zn_2/3Nb_1/3)O₃ and optimizing the preparation for viscous polymer processing (VPP), thus achieving domain engineering, enhanced relaxor behavior, and improved breakdown strength (E_b) in (Ba_0.8Sr_0.2)TiO₃-based ceramics. The broadening of the permittivity peak and highly dynamic polar nanoregions (PNRs) are correlated to expected relaxation characteristics, as indicated by the brightness of atomic position and calculated spontaneous polarization vectors determined through transmission electron microscopy. The relatively small grain size and increased band gap, verified through scanning electron microscopy and ultraviolet − visible spectrophotometry, contribute to the E_b. A prominent W_rec of 5.16 J/cm³ under 540 kV/cm and excellent temperature stability (W_rec = 3.6 J/cm³, η = 92.8%, 20–120 °C) are achieved in 0.91(Ba_0.8Sr_0.2)TiO₃ − 0.09Bi(Zn_2/3Nb_1/3)O₃ ceramics formed by VPP (BZN9_VPP). The material possesses an exceptional current density of 647.56 A/cm², a power density of 113.32 MW/cm³, and a rapid discharge speed of < 60 ns. The comprehensive outstanding performance supports the great potential of this sample for application in pulsed power capacitors.