Enhanced Energy Storage in Sn‑Substituted (Bi,Na)TiO ₃ ‐Based Thin Films via Ergodic Relaxor Stabilization

ABSTRACT

Ferroelectric capacitors face an inherent trade‐off between high maximum polarization and large remnant polarization due to domain switching dynamics, which results in low energy storage performance. The reversible transformation from an ergodic relaxor to a ferroelectric state leverages the advantages of relaxors—low remnant polarization—and ferroelectrics—high maximum polarization. In this work, Sn doping was employed to partially substitute Ti ions in the (Bi,Na,Li)TiO ₃ –Sr _0.7 Bi _0.2 TiO ₃ solid solution, stabilizing the weakly polar tetragonal ergodic relaxor phase. The increased tetragonal fraction disrupts long‐range ferroelectric order, promoting the formation of polar nanoregions and enhancing relaxor behavior. Consequently, Sn‐doped films exhibit pinched polarization‐electric field loops with increased maximum polarization and reduced remnant polarization, leading to an optimized energy storage performance with a recoverable energy density ( W _rec ) of 61 J/cm ³ and an efficiency ( η ) of 72%. These results highlight the strong potential of this material for applications in pulsed power electronics and underscore the broader utility of phase‐composition engineering in enhancing the energy storage properties of BNT‐based systems.