Self-generated semiconductor/relaxor antiferroelectric composite ceramics with high energy storage properties

In this reserch, (1- x )NaNbO ₃ - x BiFeO ₃ solid solutions were reported to clearly show relaxor antiferroelectric phase structure dependent energy storage properties, evolving from W _rec = 1.63 J/cm ³ and η =  27% in the case of x  = 0.04 at 300 kV/cm to 7.4 J/cm and 83.4% in the case of x  = 0.12 at 500 kV/cm. To further decrease the dielectric loss and improve the breakdown strength of 0.88NaNbO ₃ -0.12BiFeO ₃ ceramic, MnO ₂ was incorporated into it. In particular, When 1wt.% MnO ₂ was added, a MnFe ₂ O ₄ /0.88NN-0.12BF-Mn semiconductor/relaxor composite ceramic was unexpectedly obtained. A small amount of semiconductor second phase significantly increases the breakdown field strength of the material, thereby obtaining a super large energy storage density W _rec of 13.4 J/cm ³ and excellent energy efficiency η of 87.4% at 700 kV/cm. The finding of this study provide valuable insights of self-generated semiconductor/relaxor composite structure to obtain good energy storage performence in NaNbO ₃ -based lead-free ceramics.