From Microstructure to Macroscopic Performance: A Comprehensive Study on Low‐K Oxide‐Doped BNT–LST–NN Ceramics for Energy Storage

ABSTRACT Dielectric ceramics are popular for energy storage materials because of their rapid charge–discharge characteristics, whereas their low energy density and efficiency hinder their miniaturization and integration. In this work, the energy storage performance is significantly enhanced through introducing Al 2 O 3 and TiO 2 into the 0.425(Bi 0.5 Na 0.5 )TiO 3 –0.425(La 0.1 Sr 0.8 )TiO 3‐ δ –0.15NaNbO 3 (BNT–LST–NN) system to establish multiple coupling mechanisms. In particular, localized discrete polar regions are successfully built because of the introduction of non‐polar regions, which effectively reduces the remnant polarization. Additionally, the synergistic combination of the wide bandgap of TiO 2 and Al 2 O 3 , along with refined grain, collectively contributes to an increase in the breakdown strength ∼ of 580 kV cm. Consequently, the increased grain boundary density and secondary phase effectively hinder the propagation of breakdown pathways, enabling the material to exhibit a high recoverable energy storage density of ∼ 4.95 J cm −3 with an efficiency of ∼ 73%. Transmission electron microscope (TEM) and piezoresponse force microscopy (PFM) measurements have proved the formation of polar nano‐regions and non‐polar regions, and phase‐field simulation has revealed that the secondary phase indeed can improve the breakdown strength. This research provides a novel strategy for developing ceramic materials with superior energy storage properties.