Effective regulation of breakdown strength through the synergistic effect of defect chemistry and energy band engineering in Ba0.85Ca0.15Zr0.1Ti0.9O3-based lead-free ceramics
Abstract
Based on the fundamentals of energy storage capacitors, recoverable energy storage density (Wrec) is greatly dependent on breakdown strength (Eb). In this work, the breakdown performance of 0.92Ba0.85Ca0.15Zr0.1Ti0.9O3–0.08Bi2/3(M1/3Ta2/3)O3 (M = Mg and Zn) is significantly improved through the synergistic effect of defect chemistry and energy band engineering. The addition of A-site deficient Bi2/3(M1/3Ta2/3)O3 triggers a ferroelectric-to-relaxor ferroelectric phase transition, leading to the formation of local polar nano-regions (PNRs). More importantly, the introduction of Bi2/3(M1/3Ta2/3)O3 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 Eb. As a result, an ultrahigh Eb of ∼681.7 kV cm−1 for the 0.92Ba0.85Ca0.15Zr0.1Ti0.9O3–0.08Bi2/3(Zn1/3Ta2/3)O3 ceramic accompanied by a large maximum polarization (∼31.6 μC cm−2) contributes to a high Wrec of ∼6.93 J cm−3 and efficiency of ∼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.