Microstructure-driven excellent energy storage NaNbO3-based lead-free ceramics

Alkali niobate-based energy storage ceramics have recently drawn considerable attention because of their ultrahigh recoverable energy storage density (W rec ) and environment-friendly feature. However, it is still quite challenging for them to maintain a high energy storage efficiency (η). Herein, spark plasma sintering (SPS) technique was adopted to tailor the microstructure of Na 0.7 Bi 0.1 Nb 0.9 Ta 0.1 O 3 lead-free ceramics. Compared with their conventional sintered counterparts, the samples sintered by SPS exhibit more homogeneous microstructure, finer grains, decreased porosity and fewer oxygen vacancies. Consequently, a high breakdown strength, small remanent polarization and low polarization hysteresis give rise to excellent comprehensive energy storage performance (W rec = 6.68 J/cm 3 , η = 90.5%) of the SPS sintered ceramics. This work not only provides a potential lead-free energy storage ceramic system, but also reveals the remarkable role of the tailored microstructure in improving energy storage properties.