Achieving Ultrahigh Energy Storage Density in Lead-Free Sodium Niobate-Based Ceramics by Modulating the Antiferroelectric Phase

Lead-free antiferroelectric ceramics have drawn widespread interest recently on account of their environmentally friendly components and potential applications in high-power systems. However, their relatively low recoverable energy storage density (W-rec < 10 J/cm(3)), limited by the electric breakdown strength (Eb < 60 kV/mm), and low efficiency (eta < 80%), generated by large hysteresis during the antiferroelectric-ferroelectric phase transition, have seriously restricted their application in portable and compact electronic devices. In this study, the relaxor antiferroelectric (1- x)NaNbO3-x(0.55BiFeO(3)-0.45SrTiO(3)) ceramics were elaborately designed and systematically explored. With the help of composition regulation, the ceramics not only exhibited a stable antiferroelectric phase but also underwent a structural transformation from an antiferroelectric P (Pbma) phase to R (Pnma) phase, as confirmed by the temperature-dependent dielectric constants, Raman spectra, X-ray diffraction (XRD) refinement, pinched polarization-electric field (P-E) curves, and four-peak current-electric field (I-E) curves. In addition, the relaxor characteristic was demonstrated by the diffuse dielectric peaks, slim P-E curves, flattened Raman peaks, and I-E curves. Consequently, novel relaxor antiferroelectric ceramics were successfully obtained, which simultaneously revealed the features of relaxor and antiferroelectricity. Specifically, the Eb was significantly improved because of the reduced grain size, small sample thickness, exceptionally low dielectric loss, and a moderate dielectric constant. Finally, the sample with x = 0.12 showed an ultrahigh Wrec value of 16.2 J/cm3 and satisfactory eta of 82.3% at 97 kV/mm, outperforming most state-of-the-art counterparts. Furthermore, the ceramic also exhibited a large current density (C-D) of 1268.4 A/cm(2) and power density (P-D) of 177.6 MW/cm(3) at 28 kV/mm, offering prospective applications in high-power capacitors. This work not only achieved outstanding comprehensive energy storage performance in sodium niobate-based ceramics by modulating the antiferroelectric structure but also provided a feasible route to developing high-performance dielectric capacitors from the viewpoint of structure-property relationship.

Automated summary

In this study, relaxor antiferroelectric ceramics were designed and explored, resulting in new ceramics that combine the features of relaxor and antiferroelectricity. By regulating the composition and structure of the ceramics, the electric breakdown strength and energy storage density were improved, and the ceramics showed potential for high current and power density, offering possibilities for applications in high-power electronic devices.