Optimized energy storage performance in BF-BT-based lead-free ferroelectric ceramics with local compositional fluctuation

BiFeO3-based lead-free ferroelectric is considered a potential candidate for energy storage applications owing to its high spontaneous polarization. To tackle the compromise between high polarization and energy storage density, NaNbO3 (NN) was introduced into 0.7BiFeO3-0.3Ba(Hf0.05Ti0.95)O3 (BF-BHfT) ceramics, where Nb5+ ions enter the BF-BHfT lattices and enhance resistivity, while Na+ ions occupied on the A-sites and smash the long-range ferroelectric order into polar nanoregions. Consequently, the ceramics could maintain high maximum polarization and low remanent polarization. High recoverable energy density (Wrec) of 5.2 J/cm3 and efficiency (88%) were recorded in 0.53BF-0.3BHfT-0.17NN ceramics. Besides, it exhibited good thermostability up to 120 degrees C (Wrec variation < 5%), frequency stability from 10 to 200 Hz (Wrec variation < 7%) and excellent fatigue resistance after 104 cycles (Wrec variation < 0.2%). Under different electric fields the efficiency still maintains nearly constant. In charge-discharge test a Wdis of 3.7 J/cm3 was recorded, which proved 0.53BF-0.3BHfT-0.17NN ceramics a promising candidate for energy storage applications.