Enhanced energy storage performance of BNT-ST based ceramics under low electric field via domain engineering

Lead-free bulk ceramics for advanced pulse power capacitors possess low recoverable energy storage density (Wrec) under low electric field. Sodium bismuth titanate (Bi0.5Na0.5TiO3, BNT)-based ferroelectrics have attracted great attention due to their large maximum polarization (Pm) and high power density. The BNT-ST: xAlN ceramics are designed and fabricated to get high Wrec and large Pm under low electric field simultaneously. An excellent large Pm (49.04 μC/cm2) and Wrec (2.07 J/cm3) under low electric field (160 kV/cm) are acquired in BNT-ST: 0.1 wt% AlN. The domain structure evolution and polarization switching are investigated systematically using piezoresponse force microscopy (PFM). The introduction of AlN promotes the formation of thermal conductive network and the crystallization of ceramics, thus improving thermal stability and increasing Pm significantly. The higher density of domain walls and the larger negative built-in voltage may be beneficial to increase breakdown field strength (Eb), while the more 180° domains induce by electric field and the better domain switching behavior contribute to a significant increase in Pm. The enhanced Eb and super high Pm are favorable for obtaining high Wrec under low electric field which will boost the application of BNT-based ferroelectrics in advanced pulse power capacitors.