Outstanding comprehensive energy storage performance in lead-free BiFeO3-based relaxor ferroelectric ceramics over a wide temperature range

Breaking the polarization-breakdown strength paradox is the key to achieving high energy storage performance in lead-free relaxor ferroelectric ceramics. In this study, we propose a composition optimization strategy to break down the long-range ferroelectric polarity in the BiFeO 3 system. For (0.55- x )BiFeO 3 -0.45SrTiO 3 - x NaNb 0.85 Ta 0.15 O 3 (abbreviated as BF-ST- x NNT) lead-free ceramics, the electrical resistance and homogeneity are improved, effectively improving the breakdown durability. Simultaneously, the novel ternary ceramics changed the highest polarizability per unit volume to relaxor rather than ferroelectric. As a result, an ultra-high energy storage efficiency of 92 % and a recoverable energy storage density of 4.5 J/cm 3 are realized at a moderate electric field. Together with brilliant energy storage density stability in a wide frequency/temperature range. This study not only presents a lead-free energy storage ceramic exhibiting excellent overall performance for application in high-capacity ceramic capacitors, but also proposes a novel approach for achieving BF-based and related materials with stable performance.