Large energy-storage density in transition-metal oxide modified NaNbO3-Bi(Mg0.5Ti0.5)O3 lead-free ceramics through regulating the antiferroelectric phase structure

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, NaNbO3-Bi(Mg0.5Ti0.5)O-3 (NN-BMT) perovskite solid solutions were reported to obviously exhibit AFE phase structure dependent energy-storage performances, evolving from W-rec similar to 1.08 J cm(-3) and eta similar to 19% at x = 0.05 with an orthorhombic P phase (Pbam) under 25 kV mm(-1) to 3.12 J cm(-3) and 74%, respectively, at x = 0.08 with an orthorhombic R phase (Pnma) under 30 kV mm(-1) owing 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, CeO2 and MnO2) was found to evidently improve the sintering behaviour, bulk resistivity and defect structure, thus leading to largely enhanced dielectric breakdown strength. In particular, the MnO2 doped 0.92NN-0.08BMT sample exhibits a large W-rec of similar to 5.57 J cm(-3) and a high eta of similar to 71% as well as excellent charge-discharge performance (C-D = 636.7 A cm(-2), P-D = 63.7 MW cm(-3) and t(0.9) similar to 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.