Realizing High Comprehensive Energy Storage and Ultrahigh Hardness in Lead-Free Ceramics

Abstract

Due to the presence of pores and low density, a high recoverable energy density (<i>W</i>_rec) value is usually obtained at the cost of energy storage efficiency (η) in lead-free potassium sodium niobate [(K, Na)NbO₃, KNN] based ceramics, which also affects the hardness of ceramics, finally limiting the further development of practical applications. A high <i>W</i>_rec (∼3.60 J/cm³ ) and a high η (∼74.2%) are obtained in 0.975K_0.5Na_0.5NbO₃-0.025LaBiO₃ (0.975KNN-0.025LB) ceramics simultaneously under a high dielectric breakdown strength (DBS) of 340 kV/cm, together with a fast discharge rate (<i>t</i>_0.9 ∼ 46 ns) and high power density (<i>P</i>_D ∼ 49.4 MW/cm³). Further analysis of the intrinsic electronic structure is carried out via the first-principles calculation based on the density functional theory (DFT). An ultrahigh hardness (<i>H</i>) of 6.63 GPa can be accordingly obtained. This work combines excellent energy storage properties and ultrahigh hardness, which provides significant guidelines for applications in pulsed-power systems.