An ultrahigh energy storage density in lead-free Na 0.5 Bi 0.5 TiO 3 -NaNbO 3 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(Mg 1/3 Ta 2/3 )O 3 (SMT)-modified Na 0.5 Bi 0.5 TiO 3 NaNbO 3 (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/cm 3 ) and efficiency (∼82.24 %) at 380 kV/cm were obtained for bulk ceramics. In addition, an ultrahigh recoverable energy density (∼17.24 J/cm 3 ) 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 °C) and frequency (0.5–500 Hz) stabilities were also obtained at 600 kV/cm.