Enhanced energy storage properties in lead-free BaTiO₃@Na_0.5K_0.5NbO₃ nano-ceramics with nanodomains via a core-shell structural design

Achieving lead-free bulk ceramics with high energy storage densities has been a long-term goal pursued by researchers. Using a core-shell structural strategy, we achieved high comprehensive energy storage properties in relaxor ferroelectric BaTiO3@Na0.5K0.5NbO3 (BT@KNN) nano-ceramics (194 nm) with rhombohedral and tetragonal nanodomains. The breakdown field strength (211 kV cm(-1)) was effectively enhanced by ultrafine-grains. Maximum polarization (21.3 mu C cm(-2)) was increased and remanent polarization (3.3 mu C cm(-2)) was reduced by the nanodomain. As a result, the polarization difference reached 18.0 mu C cm(-2), thus achieving a large energy storage density of 2.24 J cm(-3) and a recoverable energy storage density of 1.90 J cm(-3) with a high energy storage efficiency of 84.8%. The ceramics exhibit excellent dielectric properties and temperature stability over a wide temperature range (-60-130 degrees C). This work may provide a theoretical basis for the realization of next generation BT-based lead-free energy storage ceramics in the future.