Synergistic effect of multi-phase and multi-domain structures induced high energy storage performances under low electric fields in Na0.5Bi0.5TiO3-based lead-free ceramics

Lead-free dielectric ceramics with ultrahigh-power density, fatigue properties, and excellent thermal stability are regarded as potential dielectric energy storage materials for the next-generation advanced pulse power capacitors. However, the large energy storage density (Wrec) and high discharging efficiency (& eta;) of dielectric capacitors are generally achieved under ultrahigh electric fields. Developing dielectric capacitors with high energy storage performances under low electric fields is of great significance. Herein, we utilized a synergistic design strategy of multi-phase and multi-domain structures to successfully synthesize the (0.65-x)(Na0.5Bi0.5)TiO3-0.35(Sr0.7Bi0.2) TiO3-xAg0.97Nd0.01Ta0.2Nb0.8O3 ((0.65-x)BNT-0.35SBT-xANTN) ceramics suitable for the low electric field situation. The formed multi-phase coexistence structure of the Rhombohedral (R3c) and Tetragonal (P4bm) phases and the elevated concentration of Bi3+ at A site in BNT-SBT-ANTN ceramics are beneficial to obtain the high maximum polarization (Pmax). Meanwhile, the introduction of ANTN in the BNT-SBT matrix can disrupt the longrange order ferroelectric domain structures and also form the local polar nanoregions (PNRs), leading to the small remnant polarization (Pr) and the improvement of the relaxation behavior. Encouragingly, the optimized 0.63BNT-0.35SBT-0.02ANTN composition exhibits excellent energy storage performances with a large Wrec of 3.61 J/cm3 and relatively high & eta; of 80.6% at a low electric field of 200 kV/cm. In addition, this 0.63BNT0.35SBT-0.02ANTN sample presents better thermal stability (20-120 celcius) and frequency stability (10-1000 Hz). Moreover, the high charge power density (PD) of 69.42 MW/cm3, the rapid discharge speed rate (& tau;0.9) of 0.22 & mu;s, and the good fatigue endurance are also achieved in the 0.63BNT-0.35SBT-0.02ANTN sample. This work may provide an effective method for designing dielectric ceramics with remarkable comprehensive energy storage performances at low electric fields to meet the requirements of advanced energy storage capacitors under extreme conditions.