Lead-free BiFeO₃-BaTiO₃ based high-T_c ferroelectric ceramics: Antiferroelectric chemical modification leading to high energy storage performance

Dielectric capacitors have been widely used in pulsed power devices owing to their ultrahigh power density, fast charge/discharge speed, and excellent stability. However, developing lead-free dielectric materials with a combination of high recoverable energy storage density and efficiency remains a challenge. Herein, a high energy storage density of 7.04 J/cm³ as well as a high efficiency of 80.5% is realized in the antiferroelectric Ag(Nb_0.85Ta_0.15)O₃-modified BiFeO₃-BaTiO₃ ferroelectric ceramic. This achievement is mainly attributed to the combined effect of a high saturation polarization (P_max), increased breakdown field (E_b), and reduction of the remnant polarization (P_r). The modification of pseudotetragonal BiFeO₃ by Ag(Nb_0.85Ta_0.15)O₃ leads to a high P_max, and the enhanced relaxor behavior gives rise to a small P_r. The promoted microstructure (such as a dense structure, fine grains, and compact grain boundaries) after modification results in a high breakdown strength. Furthermore, both the recoverable energy density and efficiency exhibit high stability over a broad range of operating frequencies (1–50 Hz) and working temperatures (25–120 ℃). These results suggest that the (0.67–x)BiFeO₃-0.33BaTiO₃-xAg(Nb_0.85Ta_0.15)O₃ ceramics can be highly competitive as a lead-free relaxor for energy storage applications.