Antiferroelectric-like BiFeO3-SrTiO3 based ceramics with high breakdown strength and energy-storage density

Herein, an outstanding excellent energy storage performance (ESP) (Wrec∼4.4 J/cm3; η∼72%; ΔP = 38.1 μC/cm2) was obtained in environmentally friendly 0.52BiFeO3-0.4SrTiO3-0.08NaNbO3 lead-free ceramic. First, the addition of NaNbO3 (NN) lead to composition and charge disorder of A- and B- sites, generating random electric field that induce the emergence of small-sized polar nano-regions (PNRs) to enhance ΔP (Pmax-Pr). Rietveld refinement analysis showed that introducing NN reduces the content of polar R3c phase from 81.8% to 24.4%, and the non-polar Pm3m phase increased. When x ≥ 0.08, the antiferroelectric-like double P-E loops were acquired due to field-induced phase transition, and further lower Pr and Ec were obtained. Then, the introduction of NN greatly improved the breakdown strength of BFO-STO ceramics. That is, enhances electrical homogeneity, increases energy gap (Eg) and refines grain size (from 1.05 to 0.75 µm). Through domain engineering, antiferroelectric-like design and other multi-factors to achieve the optimization of ESP, providing a feasible strategy for lead-free pulse energy storage capacitors. Additionally, the good temperature (20–120 °C) and frequency (1–100 Hz) stability acquired to less than 15% in favor of practical applications.