Large energy-storage density in transition-metal oxide modified NaNbO ₃–Bi(Mg _0.5Ti _0.5)O ₃lead-free ceramics through regulating the antiferroelectric phase structure

Abstract

The combination of AFE phase structural regulation and breakdown strength optimization through chemical modification leads to a large energy-storage density of W _rec∼ 5.57 J cm ⁻³in NN–BMT lead-free bulk ceramics.

Abstract

Lead-free antiferroelectric (AFE) ceramics have attracted increasing attention in recent years for application in high-power capacitors owing to both environmental friendliness and high energy density. However, the relevant research progress has been seriously restricted by the limited amount of AFE candidate materials with low cost and excellent properties, which significantly rely on the AFE phase stability and crystal symmetry. In this work, NaNbO ₃–Bi(Mg _0.5Ti _0.5)O ₃(NN–BMT) perovskite solid solutions were reported to obviously exhibit AFE phase structure dependent energy-storage performances, evolving from W _rec∼ 1.08 J cm ⁻³and η∼ 19% at x= 0.05 with an orthorhombic P phase ( Pbam) under 25 kV mm ⁻¹to 3.12 J cm ⁻³and 74%, respectively, at x= 0.08 with an orthorhombic R phase ( Pnma) under 30 kV mm ⁻¹owing to the transition of square-like double hysteresis loops into slim and double-like ones and the increased testable electric fields. Most interestingly, doping 0.5 mol% transition-metal oxides (CuO, CeO ₂and MnO ₂) was found to evidently improve the sintering behaviour, bulk resistivity and defect structure, thus leading to largely enhanced dielectric breakdown strength. In particular, the MnO ₂doped 0.92NN–0.08BMT sample exhibits a large W _recof ∼ 5.57 J cm ⁻³and a high ηof ∼ 71% as well as excellent charge–discharge performance ( C _D= 636.7 A cm ⁻², P _D= 63.7 MW cm ⁻³and t _0.9∼ 85 ns), determined by means of the detailed analysis of the grain size distribution, impedance and X-ray photoelectron spectra. The results demonstrate that NN–BMT bulk ceramics could be very competitive lead-free AFE materials for energy-storage capacitors in pulsed power devices.