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 (Wrec) of 2.42 J cm−3 (low electric field of E = 143 kV cm−1) in {Bi0.5[(Na0.8K0.2)0.90Li0.10]0.5}0.96Sr0.04(Ti0.975Ta0.025)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 Wrec ≤ 0.047% after 105 cycles and Wrec > 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.