Achieving high energy-storage density in K0.5Na0.5NbO3 optimized Bi0.25Na0.25Ba0.15Sr0.35TiO3 relaxor ferroelectric ceramics

Lead-free ceramics with high energy-storage density and dielectric stability are attracted considerable attention to address low-driven energy storage electronic fields. Here, the Bi0.25Na0.25Ba0.15Sr0.35TiO3 + K0.5Na0.5NbO3 (BNBST + Kx, x = 0, 2, 4, 6, 8, 10) ceramics were constructed to systematically investigate. All BNBST + Kx ceramics exhibited single pseudocubic perovskite structure with high bulk density. High energy storage density Wtotal = 2.3 J/cm3, recoverable energy storage density Wrec = 1.91 J/cm3 and efficiency η = 84% under 117 kV/cm were achieved at x = 4, and the value of 1.91 J/cm3 was superior compared with most Wrec in lead-free bulk ceramics under a relatively low electric field (< 150 kV/cm), while the dielectric temperature stability was boosted to meet wider working window. Moreover, the BNBST + K4 ceramics displayed satisfactory frequency (1–100 Hz), anti-fatigue (1–104 cycle times) and temperature (20–200 °C) dependent energy storage stability, which might be a powerful contender for low-voltage driven ceramic capacitors of high energy-storage density.