Combinatorial Optimization of Grain Size and Domain Morphology Boosts the Energy Storage Performance in (Bi_0.5Na_0.5)TiO₃-Based Dielectric Ceramics

Lead-free dielectric ceramics exhibiting excellent energy storage capacity, long service life, and good safety have been considered to have immense prospects in next-generation pulsed power capacitors. However, it is still challenging to simultaneously achieve large recoverable energy density (<i>W</i>_rec), high efficiency (η), and excellent charge-discharge performance. Herein, we fabricated lead-free (1 - <i>x</i>)(Bi_0.5Na_0.5)TiO₃-<i>x</i>(Sr_0.7Bi_0.1La_0.1)TiO₃ ((1 - <i>x</i>)BNT-<i>x</i>SBLT) dielectric ceramics, and a good balance between <i>W</i>_rec ∼ 4.15 J/cm³ and η ∼ 93.89% under 333 kV/cm, as well as superior charge-discharge properties (power density <i>P</i>_D ∼ 185.42 MW/cm³, discharge energy density <i>W</i>_d ∼ 2.2 J/cm³, and discharge time <i>t</i>_0.9 ∼ 53.8 ns under 250 kV/cm), was achieved in 0.6BNT-0.4SBLT ceramics. The good energy storage performance can be attributed to the synergistic contributions of significantly enhanced <i>E</i>_b caused by grain refinement and the large Δ<i>P</i> values induced by polar nanoregions (PNRs) under a high external electric field. Moreover, the 0.6BNT-0.4SBLT ceramics also present excellent temperature stability of energy storage properties (the variations of <i>W</i>_rec and η less than 0.45% and 0.14%, respectively) over a temperature range of 25-185 °C. These figures of merit make 0.6BNT-0.4SBLT ceramics the most promising candidate for energy storage capacitors in advanced pulse power systems.