Grain size modulated (Na0.5Bi0.5)0.65Sr0.35TiO3-based ceramics with enhanced energy storage properties

Ferroelectric ceramics, as a potential candidate for high-power energy storage capacitors, lies in their excellent recoverable energy storage density (Wrec) and outstanding efficiency (η) in practical applications. Herein, a new type of lead-free ceramics (1-x)(Na0.5Bi0.5)0.65Sr0.35TiO3-xBiMg0.5Sn0.5O3 or (1-x)NBST-xBMS was prepared with the aim of enhancing the breakdown strength (Eb) and reducing the energy storage loss through grain refinement. It was found that Eb of 0.9NBST-0.1BMS reaches 405 kV/cm due to the reduction in the grain size of ceramic and thus the extremely high ratio of grain boundary resistance to grain resistance. Besides, a remarkable energy-storage performance was obtained, that is, Wrec and η are ∼ 6.68 J/cm3 and 89.1% at 405 kV/cm, respectively, along with excellent stability in terms of frequency, temperature, and fatigue endurance. The outstanding energy-storage performance is resulted from modulating the grain size via doping the moderate content of Bi3+ and Mg2+/Sn4+, which is beneficial to increase the breakdown field by increasing resistivity under high electric field while increasing the grain boundary activation energy and promote the formation of a relaxor state at the same time. More importantly, energy storage potential (defined as Wrec/Eb) is up to 0.01649 μC/cm2, being the highest value reported so far for BNT-based ceramics in energy-storage application. Our results pave the way for practical applications of NBST-based ferroelectric capacitors with excellent energy storage performance.