Effective regulation of breakdown strength through the synergistic effect of defect chemistry and energy band engineering in Ba_0.85Ca_0.15Zr_0.1Ti_0.9O ₃-based lead-free ceramics

Based on the fundamentals of energy storage capacitors, recoverable energy storage density (W-rec) is greatly dependent on breakdown strength (E-b). In this work, the breakdown performance of 0.92Ba(0.85)Ca(0.15)Zr(0.1)Ti(0.9)O(3)-0.08Bi(2/3)(M1/3Ta2/3)O-3 (M = Mg and Zn) is significantly improved through the synergistic effect of defect chemistry and energy band engineering. The addition of A-site deficient Bi-2/3(M1/3Ta2/3)O-3 triggers a ferroelectric-to-relaxor ferroelectric phase transition, leading to the formation of local polar nano-regions (PNRs). More importantly, the introduction of Bi-2/3(M1/3Ta2/3)O-3 into Ba0.85Ca0.15Zr0.1Ti0.9O3 effectively increases the band gap of samples and reduces grain growth and leakage current density by inhibiting the formation of oxygen vacancies, thus enhancing E-b. As a result, an ultrahigh E-b of similar to 681.7 kV cm(-1) for the 0.92Ba(0.85)Ca(0.15)Zr(0.1)Ti(0.9)O(3)-0.08Bi(2/3)(Zn1/3Ta2/3)O-3 ceramic accompanied by a large maximum polarization (similar to 31.6 mu C cm(-2)) contributes to a high W-rec of similar to 6.93 J cm(-3) and efficiency of similar to 82%. Furthermore, all these ceramics exhibited excellent thermal/frequency stability and charge-discharge performances. These findings suggest that defect chemistry and energy band engineering is an effective strategy for developing novel lead-free relaxor ferroelectric ceramics.