An ultrahigh energy storage density in lead-free Na0.5Bi0.5TiO3-NaNbO3 based ceramics via multiple optimization strategies

Currently, dielectric capacitors with superior charge-discharge performance, long lifetime, and high power density are drawing increasing attention, especially for lead-free ferroelectrics due to their environmental friendliness, multi-functional applications and excellent energy storage properties. In this work, lead-free relaxor ferroelectric Sr(Mg1/3Ta2/3)O3 (SMT)-modified Na0.5Bi0.5TiO3-NaNbO3 (NBT-NN) bulk and thick film ceramics were prepared via solid -state reaction and tape-casting approaches, respectively, and their energy storage characteristics were tailored via multiple optimization strategies. A high recoverable energy density (-5.20 J/ cm3) and efficiency (-82.24 %) at 380 kV/cm were obtained for bulk ceramics. In addition, an ultrahigh recoverable energy density (-17.24 J/cm3) with a high efficiency (-82.02 %) at 1200 kV/cm was obtained in thick film ceramics, which are attributed to the improvement of dielectric breakdown strength (DBS) and the transformation to the relaxor ferroelectrics. Moreover, the excellent temperature (30-130 degrees C) and frequency (0.5-500 Hz) stabilities were also obtained at 600 kV/cm.