Self-Generated Semiconductor/Relaxor Antiferroelectric Composite Ceramics with High Energy Storage Properties

Abstract

NaNbO3-based ceramics show promising application prospects in the field of dielectric energy storage due to thier advantages of non-toxic, light weight and low cost. However, AFE orthorhombic P phase in NaNbO3 ceramics will transforms into FE orthorhombic Q phase irreversibly under external electric field. This will result in a great hysteresis of polarization-electric field loop, greatly reducing energy storage performence. In this reserch, (1-x)NaNbO3-xBiFeO3 solid solutions were reported to clearly show relaxor antiferroelectric phase structure dependent energy storage properties, evolving from Wrec = 1.63 J/cm3 and η = 27% in the case of x = 0.04 with an orthorhombic P (Pbam) phase at 300 kV/cm to 7.4 J cm-1 and 83.4% in the case of x = 0.12 with an orthorhombic R (Pnma) phase at 500 kV/cm. Moreover, excellent frequency and temperature stabilities (variation of Wrec<2% after 0.5-500 Hz, Wrec<5% over 20-100 °C) were observed. To further decrease the dielectric loss and improve the breakdown strength of 0.88NaNbO3-0.12BiFeO3 ceramic, MnO2 was incorporated into it to optimize the energy-storage performance. In particular, When 1% MnO2 was added, a 0.88NN-0.12BF-Mn/MnFe2O4 relaxor/semiconductor 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 Wrec of 13.4 J/cm3 and excellent energy efficiency η of 87.4% at 700 kV/cm. The finding of this study provide valuable insights of self-generated relaxor/semiconductor composite structure to obtain good energy storage performence in NaNbO3-based lead-free ceramics.

Keywords: Relaxor antiferroelectric, Composite, Energy Storage, NaNbO3, Lead-free