Enhanced energy storage properties in lead-free BaTiO3@Na0.5K0.5NbO3 nano-ceramics with nanodomains via a core–shell structural design

Abstract

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@Na_0.5K_0.5NbO₃ (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 μC cm⁻²) was increased and remanent polarization (3.3 μC cm⁻²) was reduced by the nanodomain. As a result, the polarization difference reached 18.0 μC 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 °C). This work may provide a theoretical basis for the realization of next generation BT-based lead-free energy storage ceramics in the future.