Ultra-stable dielectric properties and enhanced energy storage density of BNT-NN-based ceramics via precise core-shell structure controlling

High discharge-energy-storage-density (Wdis) at low electric field is in high demand for advanced ceramics. In this work, a core-shell structure is well constructed and meticulously adjusted to enhance the energy storage properties. The meticulous control of the coating layer can effectively improve the breakdown strength (Eb), ensure a high polarization, and achieve a significant optimization of temperature stability, simultaneously. Compared with 0.78Bi0.5Na0.5TiO3-0.22NaNbO3 (BNTNN) ceramics without coating layer, the BNTNN@0.8 wt%SiO2 ceramics achieve an inspiring improvement of 50 % in Eb, which is benefit from the finer grains and the enhanced band gap. Notably, the BNTNN@0.8 wt%SiO2 ceramics obtain a superior Wdis of 6.17 J/cm3 at 330 kV/cm. Importantly, BNTNN@0.8 wt%SiO2 ceramics display an ultra-stable temperature stability with a high dielectric of 1350 ± 2.5 % over a wide temperature range from 35 to over 400 °C. The meticulous control of core-shell structure is expected to be a general and effective way to improve the energy-storage performance of diverse dielectric ceramics. •The high breakdown strength and high polarization are achieved by a core-shell structure controlling strategy.•A large Wdis of 6.17 J/cm3 was obtained in BNTNN@0.8 wt%SiO2 ceramics at a relatively low electric field of 330 kV/cm.•BNTNN@0.8 wt%SiO2 ceramics display an ultra-stable temperature stability with εr of 1350 ± 2.5 % from 35 to 400 °C.