Multi-scale domain enhanced energy storage performance in lead-free Bi_0.5Na_0.5TiO₃-based complex perovskites with low sintering temperature

Eco-Friendly perovskite ceramics, particularly the Bi_0.5Na_0.5TiO₃ (BNT)-based materials, possessing a wide range of applications including energy storage. In this work, the multi-scale domain structures with enhanced energy-storage performance are achieved in the relaxor-ferroelectric Bi_0.5Na_0.5TiO₃−Bi(Zn_0.5Hf_0.5)O₃ (BNT−BZH) ceramics, along with high polarization strength and substantial structural tolerance. The introduction of BZH significantly reduces the sintering temperature of the BNT-based ceramics (≤975 °C), accompanied by an enhancement of the relaxation behaviors. The characterizations of transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) indicate that BZH induces multi-scale ferroelectric domains, thereby improving the energy storage properties of the matrix. The thermally stimulated depolarization current (TSDC) tests reveal that oxygen vacancies are the main types of defects within the BNT−BZH ceramics, which can induce the leakage conductance and affect the breakdown field strength consequently. Ultimately, the 0.85BNT−0.15BZH ceramics can be well-sintered at 975 °C, exhibiting a high recoverable energy density (W_rec) of 2.49 J/cm³ at 230 kV/cm with a moderate efficiency (η) of 61.5 %, an extremely rapid discharge rate (t_0.9–45.5 ns) and a high power density (160 kV/cm, 44.84 MW/cm³). These findings are beneficial for the development of low-temperature sintered lead-free ferroelectric materials for applications in energy storage.