Superior comprehensive energy storage in high-entropy Lead-free quasi-linear Relaxor ceramics by local heterogeneous polarization.

Dielectric ceramic capacitors show exceptional promise for applications in electrical and electronic equipment, but the parallel attainment of a high recoverable energy density (W)/efficiency (η) and superior stability poses a significant barrier for the practical application of pulse power capacitors. Herein, we report a novel, lead-free, quasi-linear, high-entropy (CaBiNa)(TiHfAlTa)O (CBNTHATx, x = 0, 0.15, 0.2, 0.25, and 0.3) ceramic fabricated by entropy tuning. Local polarity fluctuations and microstructural evolution were manipulated by designing complex high-entropy matrices to induce polar nanoregions (PNRs), local structural heterogeneity, and highly stable local structures, which facilitate a dynamic polarization response and high polarization. Consequently, the CBNTHAT0.25 ceramic can deliver a large recoverable energy density (W ∼ 7.12 J cm), concurrent with an ultrahigh energy storage efficiency (η ∼ 94.8 %) and hardness (H ∼ 8.11 GPa), as well as superior temperature/frequency stabilities and excellent discharging properties (power density P approximately 241.71 MW cm and discharge speed t approximately 22.93 ns), surpassing the comprehensive energy storage performance of previously reported linear CaTiO-based systems. This study emphasizes the feasibility of high-entropy strategies for quasi-linear dielectric ceramics, heralding promising advances in ceramic capacitors with integrated energy storage performance.