Enhancing energy storage density in lead-free BiFeO3-based relaxor ferroelectric ceramics through multiple optimization designs

Abstract

Environmentally friendly BiFeO₃–BaTiO₃ based dielectric capacitors are expected to be promising candidates in energy storage applications. Nevertheless, the trade-off between various parameters, such as maximum polarization P_max, remnant polarization P_r, and dielectric breakdown strength E_b, restricts the further improvement of the energy storage properties of dielectric ceramics. Herein, a high recoverable energy storage density (9.72 J cm⁻³) and a high efficiency (72%) at 610 kV cm⁻¹ are simultaneously obtained in (0.7−x)BiFeO₃−0.3BaTiO₃−xCa(Cr_0.5Nb_0.5)O₃ (BF–BT–xCCN) ceramics by introducing nanodomain-engineering. Lead-free ceramic capacitors exhibit ultra-high energy storage performance under high electric fields. E_b of the BiFeO₃–BaTiO₃ based ceramics is significantly enhanced, mainly due to the increased band gap, the refined grain size, and the improved resistivity with the substitution of Ca(Cr_0.5Nb_0.5)O₃. More importantly, the BF–BT–0.2CCN ceramic exhibits excellent thermal stability (±10%, −50 to 250 °C), frequency stability (1100 Hz), and fast discharge rate (t_0.9∼0.0308 μs). These results indicate that BF–BT–xCCN ceramics are promising dielectric energy storage materials.