A-/B-site engineering of AgNbO <sub>3</sub> -based ceramics for high-efficiency relaxor antiferroelectric energy storage
Seonhwa Park, Seok Hwan Kim, C. Lee, Gyeongbok Yang, Hyunseok Song, Geon‐Tae Hwang, Mahesh Peddigari, Jong Wook Roh, Jungho Ryu, Yuho Min
Abstract
Lead-free antiferroelectric (AFE) ceramics are promising candidates for next-generation pulsed power capacitors. However, their practical deployment remains limited by low recoverable energy density (<em>W<sub>rec</sub></em>), limited dielectric breakdown strength (<em>E<sub>b</sub></em>), and poor efficiency (<em>η</em>), particularly under moderate electric fields. To address these challenges, this study introduces a compositional design strategy that simultaneously engineers both A- and B-sites in AgNbO<sub>3</sub> (AN) perovskite ceramics. Specifically, 20 mol% Ta<sup>5+</sup> is fixed at the B-site while dual A-site substitution with Li<sup>+</sup> and Nd<sup>3+</sup> is implemented. This co-doping approach enables a tunable transition from a conventional AFE behavior to a relaxor-antiferroelectric-like (R-AFE-like) state. This evolution is primarily driven by A-site chemical disorder introduced by Li<sup>+</sup>/Nd<sup>3+</sup> co-doping, which disrupts long-range antiferroelectric ordering and facilitates the formation of nanodomains. In parallel, B-site Ta<sup>5+</sup> substitution contributes by suppressing octahedral tilting and stabilizing the nonpolar phase. The optimized composition, (Ag<sub>1-4x</sub>Li<sub>x</sub>Nd<sub>x</sub>)(Nb<sub>0.8</sub>Ta<sub>0.2</sub>)O<sub>3</sub> at x = 0.03, delivers a remarkable recoverable energy density of 7.2 J/cm<sup>3</sup> and an efficiency of 92.3% under a moderate electric field of 327 kV/cm. In addition, this composition demonstrates an excellent <em>W<sub>rec</sub>/E<sub>b</sub></em> ratio and capacitor-grade reliability, including strong frequency and thermal stability, as well as ultrafast discharge characteristics (<em>t<sub>0.9</sub></em> ~ 40 ns) with a peak power density of 172 MW/cm<sup>3</sup>. Overall, this work provides a detailed structure-property-performance framework for designing high-efficiency, high-power, lead-free capacitors by harnessing tunable relaxor-antiferroelectricity.