Superior energy-storage performances achieved in NaNbO3-based antiferroelectric ceramics by phase-structure and relaxation regulation

Lead-free NaNbO3-based antiferroelectric (AFE) ceramics are highly considered as promising substitutes of leadbased ones in dielectric energy-storage field. However, their low breakdown strength and large electric hysteresis loss originating from the field-induced metastable ferroelectric (FE) Q phase and/or AFE P phase still remains challenging, which severely impedes the further improvement of energy-storage performances. Herein, an effective phase-structure and relaxation regulation via A-site cation substitution strategy has been proposed to solve this issue. The phase-structures of the designed NN-based AFE ceramics evolve from orthorhombic P phase to R phase accompanying with the enhancement of relaxation behavior. Accordingly, an effective transformation from a plump and pinched polarization-electric field (P-E) hysteresis loop to a slim and slanted one has undergone, contributing to superior energy-storage performances. Noticeably, an expected large recoverable energy density (Wrec) of 4.0 J/cm3 with a high energy conversion efficiency (eta) of 80.0 % was realized in 0.94 (Na0.88Sm0.04NbO3)-0.06(BiFeO3) relaxor AFE ceramics at 460 kV/cm. Meanwhile, a great discharge energy density (Wdis) of 1.2 J/cm3 and a large power density (PD) of 92.4 MW/cm3 were achieved at 200 kV/cm. Furthermore, the favorable functional reliabilities in frequency, temperature, and fatigue cycle were also confirmed. These results not only demonstrate the great potential of NaNbO3-based relaxor AFE ceramics for dielectric energy-storage applications, but also confirm the validity of the strategy proposed in this work to obtain superior energy-storage performances.