Unlocking Superior Energy Storage: Multiscale Optimized BNT‐Based Capacitors for Low‐Field Applications
Amiya Mandal, Shivam Kumar Mittal, Deepanshu Kaneria, K. L. Yadav
Abstract
Abstract Achieving superior energy storage performance in dielectric materials under low electric fields remains a challenge. Most recent advancements require high fields that limit device applicability. Developing dielectric capacitors with high recoverable energy density ( W rec ), efficiency ( η ), and energy‐storage coefficient ( W rec / E ) at low/moderate fields is critical for safer, compact, and durable electronics. To address this, lead‐free BNT‐based {(1− x )(Bi 0.5 Na 0.5 )(Ti 0.7 Zr 0.3 )O 3 ‐ x (Sr 0.7 Bi 0.2 )TiO 3 } is optimized, abbreviated as (1− x )BNZT‐ x SBT, solid solutions using multi‐scale regulations to achieve a giant W rec / E . This approach modulates the rhombohedral (R)/tetragonal (T) phase ratio, refines grains, and induces polymorphic polar nanoregions (PNRs) through a macrodomain‐to‐nanodomain transition. SBT incorporation also raises activation energy, broadens band‐gap energy, and suppresses interfacial polarization, enhancing breakdown strength. The optimized 0.7BNZT‐0.3SBT ceramic delivers an exceptionally high W rec / E of 0.021 mC cm −2 and W rec of ≈4.3 J cm −3 at 204 kV cm −1 , surpassing most recently developed dielectric bulk ceramics. Although a high η ≈ 97.52% is achieved at x = 0.4, all energy storage parameters are best at x = 0.3. Additionally, the material shows excellent stability across a wide temperature (≈160 °C) and frequency (≈150Hz) range and strong fatigue resistance (≈10 4 cycles). These findings highlight the potential and effectiveness of this BNT‐based ceramic for highly efficient capacitors in low electric field applications.