Phase and Band Structure Engineering via Linear Additive in NBT-ST for Excellent Energy Storage Performance with Superior Thermal Stability.

Lead-free relaxor ferroelectric ceramics with ultrahigh energy-storage performance are vital for pulsed power systems. We herein propose a strategy of phase and band structure engineering for high-performance energy storage. To demonstrate the effectiveness of this strategy, (1 - x )(0.75Na 0.5 Bi 0.5 TiO 3 -0.25SrTiO 3 )- x CaTi 0.875 Nb 0.1 O 3 (NBT-ST- x CTN, x = 0.1, 0.2, 0.3, 0.4, and 0.5) samples were designed and fabricated via the solid-state reaction method. The linear dielectric CTN was used as a modulator to tune both phase and band structures of the tested system. Our results show that both rhombohedral phase ( R- phase) and tetragonal phase ( T- phase) coexist in the samples. The R / T ratio decreases, while the band gap increases with increasing CTN content. The best energy-storage properties with large energy storage density ( W rec = 7.13 J/cm 3 ), a high efficiency (η = 90.3%), and an ultrafast discharge time (25 ns) were achieved in the NBT-ST-0.4CTN sample with R / T = 0.121. Importantly, along with its excellent energy-storage performance, the sample exhibited superior thermal stability with the variations of W rec ≤ 7% and η ≤ 10% over the wide temperature range of 233-413 K. This work suggests that this engineering of phase and band structures is a promising strategy to achieve superior energy-storage properties in lead-free ceramics.