Microstructure effects on the energy storage density in BiFeO3-based ferroelectric ceramics

Lead-free BiFeO 3 –BaTiO 3 –Bi(Mg 2/3 Nb 1/3 )O 3 (BFBT-BMN) ceramics with different grain sizes were fabricated by using a conventional solid-state reaction. The high-energy ball milling technique was utilized to obtain the fine-grained ceramics. The grain size reduction lowers the remanent polarization ( P r ) and enhances the dielectric breakdown strength ( E b ) leading to a drastic increase of the recoverable energy storage density ( W re ). For the fine-grained BFBT-BMN ceramics, W re greatly increases by 8 times from 0.16 J/cm 3 to 1.27 J/cm 3 , compared to the coarse-grained BFBT-BMN ceramics. Transmission electron microscopy (TEM) and piezo-response force microscopy (PFM) measurements revealed the occurrence of the polar nanoregions (PNRs) in the fine-grained BFBT-BMN ceramics. The dynamic and weakly correlated PNRs structure is responsible for the enhancement of recoverable energy storage density in the fined-grained BFBT-BMN ceramics. This work indicates that the grain size reduction is an effective way to modify the energy storage properties of BiFeO 3 -based ferroelectric ceramics .