Greatly enhanced discharge energy density and efficiency of novel relaxation ferroelectric BNT-BKT-based ceramics

The development of lead-free bulk ceramics with high recoverable energy density ( W rec ) and high efficiency plays a major role in meeting the requirements for miniaturization and integration of advanced pulsed power capacitors. In this study, composition-dependent phase structures and ferroelectric properties of lead-free relaxor ferroelectric ceramics (1 − x )(0.84Bi 0.5 Na 0.5 TiO 3 -0.16K 0.5 Bi 0.5 TiO 3 )- x (Bi 0.2 Sr 0.7 TiO 3 ) [(1 − x )(BNT-KBT)- x SBT, x = 0-0.45] are investigated. The introduction of SBT into the morphotropic phase boundary (MPB) BNT-BKT system constructs the relaxor ferroelectrics according to the order-disorder theory, leading to an improved energy storage performance. Results show that an ultrahigh recoverable energy density of 4.06 J cm −3 and a high energy-storage efficiency of 87.3% under an electric field of 350 kV cm −1 are achieved concomitantly, together with a superior high temperature stability (30-160 °C) and strong fatigue endurance (10 4 cycles). In particular, the corresponding ceramic exhibits an ultrafast discharge rate ( τ 0.9 = 127 ns) and a high level of discharge energy density ( U dis = 1.29 J cm −3 ). Our study provides the groundwork for an effective way to design high-performance ceramics for application in next generation energy storage capacitors. The 0.65(NBT-BKT)-0.35SBT ceramic possesses an ultra-high recoverable energy storage density ( W rec ∼ 4.06 J cm −3 ) and maintains a relatively high efficiency ( η = ∼87.3%).