Energy storage performance of Bi_0.5Na_0.5TiO₃-based relaxor ferroelectric ceramics with superior temperature stability under low electric fields

Dielectric ceramics are highly favorable for pulsed power applications owing to their ultra-fast charge-discharge speed and excellent reliability. However, their low energy density under low electric fields remains as a bottleneck for them to be employed in integrated electronic devices with shrinking dimensions. In this work, we have designed a comprehensive strategy to synthesize lead-free (Bi_1/2Na_1/2)_1−xSr_xTi_0.98(Fe_1/2Nb_1/2)_0.02O₃ (BNT-xST-2FN, x = 0.30, 0.35, 0.40 and 0.45) ceramics via traditional solid-state method. On one hand, the hybridizations of Bi³⁺ orbitals and the displacement of B-site cations under the applied electric field lead to a high polarization. On the other hand, the (Fe_1/2Nb_1/2)⁴⁺ complex-ion and SrTiO₃ were introduced to improve the relaxor behavior of the system, resulting in a high energy-storage efficiency. In this way, an excellent energy density of 3.36 J/cm³ and a high energy efficiency of 81% are simultaneously achieved in the BNT-0.40ST-0.02FN composition under a low electric field of 170 kV/cm, which is superior to other BNT-based materials under similar electric fields. Moreover, the ceramic exhibits a superior thermal stability (25–200 °C). This work provides a promising approach for designing high-performance lead-free energy storage ceramics under low electric fields.