Achieving outstanding energy storage behaviors via combinatorial optimization design in BNT-based relaxor ferroelectric ceramics under medium–low electric fields

Abstract

As the development of electronic components has become highly integrated and diversified, dielectric ceramic energy storage capacitors have attracted wide attention due to their high-power density, low cost and ability to operate at high temperatures. In this work, we have designed (0.8 − x)Bi_0.5Na_0.5TiO₃–0.2BaZr_0.3Ti_0.7O₃–xNaNbO₃ (abbreviated as (0.8 − x)BNT–0.2BZT–xNN) lead-free relaxor ferroelectric ceramics and successfully optimized the energy storage performance by synergistically modifying critical factors affecting energy storage properties. The 0.7BNT–0.2BZT–0.1NN ceramic achieved high maximum polarization (P_max = 42.1 μC cm⁻²), extremely low remnant polarization, recoverable energy storage density (W_rec = 3.53 J cm⁻³), efficiency (η = 93.5%) and W_rec/E = 160.45 J (kV m⁻²) under a medium–low electric field (E = 220 kV cm⁻¹). The simultaneous achievement of high energy storage density and efficiency under lower electric fields is due to the expansion of the octahedral framework facilitated by Ba²⁺ and Zr⁴⁺, which promotes ion displacement. NaNbO₃ can further improve relaxor behaviors, compensating for polarization losses caused by relaxation and enhancing breakdown field strength. Furthermore, it also exhibits excellent electric field stability (30–220 kV cm⁻¹, Δη < 0.7%), thermal stability (20–140 °C, ΔW_rec < 7.2%), and frequency stability (1–100 Hz, ΔW_rec < 5.3%). This work provides an option for the selection of dielectric capacitors under limited electric field conditions.