Ultrahigh energy-storage potential under low electric field in bismuth sodium titanate-based perovskite ferroelectrics

Abstract

Relaxor ferroelectrics are receiving an increasing amount of attention because of their superior energy-storage density. Due to environmental concerns, lead-free alternatives are highly desirable, with bismuth sodium titanate highlighted for its energy-storage applications. Here, we realized an enhancement in energy-storage performance with a recoverable energy density (W_rec) of 2.42 J cm⁻³ (low electric field of E = 143 kV cm⁻¹) in {Bi_0.5[(Na_0.8K_0.2)_0.90Li_0.10]_0.5}_0.96Sr_0.04(Ti_0.975Ta_0.025)O₃ ceramics by a hot-pressed sintering (HPS) method, which is greatly superior to the reported perovskite ceramics under similar electric fields. In addition, excellent fatigue and thermal stabilities (variation of W_rec ≤ 0.047% after 10⁵ cycles and W_rec > 2 J cm⁻³ over 25–175 °C) can be observed. The HPS method greatly increases the dielectric breakdown strength (DBS ∼ 143 kV cm⁻¹) because of a denser structure consisting of large and small grains, which is superior to those (78–97 kV cm⁻¹) of spark plasma sintering (SPS), conventional air sintering (CAS), and MnO aids sintering (AS) methods. In addition to the contribution of the enhanced breakdown strength, the ultrahigh energy-storage density is also due to the almost complete RE to FE transition resulting from strain, polarization, and current density versus electric field (S–E, P–E, j–E) loops. Interestingly, a giant strain of 0.65% can also be found by the HPS method. In particular, a conceptual model based on the nature of relaxor ferroelectrics is employed to understand the excellent energy-storage properties observed in this work. We believe that the findings in this work may provide future tips and guidance for this direction of study.