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

Abstract

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(Nb0.85Ta0.15)O3-modified BiFeO3-BaTiO3 ferroelectric ceramic. This achievement is mainly attributed to the combined effect of a high saturation polarization (Pmax), increased breakdown field (Eb), and reduction of the remnant polarization (Pr). The modification of pseudotetragonal BiFeO3 by Ag(Nb0.85Ta0.15)O3 leads to a high Pmax, and the enhanced relaxor behavior gives rise to a small Pr. 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 °C). These results suggest that the (0.67–x)BiFeO3-0.33BaTiO3-xAg(Nb0.85Ta0.15)O3 ceramics can be highly competitive as a lead-free relaxor for energy storage applications.