Entropy‐Engineered Topological Relaxor States in Lead‐Free Ferroelectric Superlattices for High‐Performance Capacitive Energy Storage

ABSTRACT Dielectric capacitors are essential components in advanced power electronics, but their energy‐storage performance is constrained by the trade‐off between reversible polarization and dielectric breakdown strength. Although ferroelectric/paraelectric superlattices that stabilize topological polar domains offer a promising route to low‐hysteresis switching and enhanced breakdown resistance, the thick paraelectric layers required to maintain these states inevitably cause severe polarization dilution. Here, we propose a synergistic strategy that integrates topological superlattice architecture with moderate entropy engineering in lead‐free Na 0.5 Bi 0.5 TiO 3 /SrTiO 3 superlattices. Phase‐field simulations reveal that local random fields transform continuous vortices into topological relaxor states, effectively flattening the thermodynamic energy barriers for field‐induced phase transitions. This mechanism enables thinner paraelectric layers to suppress remnant polarization while retaining high maximum polarization, overcoming the polarization‐dilution bottleneck. Furthermore, the introduced structural and energetic fluctuations deflect and branch dielectric breakdown pathways, markedly increasing their tortuosity and high‐field endurance. Consequently, the optimized synergistic superlattice yields a superior theoretical recoverable energy density alongside robust field, temperature, and frequency stability. This work establishes a microscopic physical framework for tailoring topological phase transitions and provides practical design guidelines for next‐generation lead‐free dielectric capacitors.