Ultrahigh energy storage performance of a 0.75Bi0.47Na0.47Ba0.06TiO3-0.25CaTi0.8Sn0.2O3 ceramic under moderate electric fields

Abstract

The development of ceramic capacitors featuring high reliability and superior comprehensive performance is vital for practical applications in medium electric fields. In this work, a synergistic strategy was proposed to improve the energy storage performance of (1 − x)0.94Bi_0.47Na_0.47Ba_0.06TiO₃-xCaTi_0.8Sn_0.2O₃ ((1 − x)BNBT-xCTS) ceramics by introducing polymorphic nanodomains and transforming rhombohedral (R3c) to tetragonal (P4bm) forms, exhibiting a superparaelectric state at room temperature (RT). Remarkably, a lead-free 0.75Bi_0.47Na_0.47Ba_0.06TiO₃-0.25CaTi_0.8Sn_0.2O₃ (0.75BNBT-0.25CTS) ceramic exhibits superior energy storage properties: W_rec = 5.81 J cm⁻³ and η = 90.5% at a moderate field of 315 kV cm⁻¹, along with promising frequency/temperature stability (1–200 Hz and 20–200 °C) as well as a fast discharge rate (t_0.9) of 72 ns. Additionally, the sample of 0.75Bi_0.47Na_0.47Ba_0.06TiO₃-0.25CaTi_0.8Sn_0.2O₃ shows excellent dielectric constant and thermal stability (Δε′/ε′_{25 °C} ≤ ±15% at 1 kHz) in the range of −120 to 204 °C, satisfying the XR9-type capacitor. This study shows that the construction of polymorphic nanodomains and superparaelectric states at RT is an effective strategy to obtain high-efficiency energy storage ceramics under medium electric fields.