Structural evolution and energy storage performance in SBLT-based thin films by high-entropy engineering

Dielectric capacitors are indispensable for pulsed-power systems due to their ultrahigh power density, yet their widespread application is limited by low recoverable energy density ( W rec ). High-entropy engineering offers a promising strategy to synergistically enhance polarization and breakdown strength ( E b ). Here we introduce an equimolar mixture of Zr, Al, Hf, and Sb (ZAHS) into the B-site of SrBi 3.25 La 0.75 Ti 4 O 15 (SBLT) thin films. With increasing ZAHS content ( x = 0–0.5), the films undergo a phase evolution from a single Aurivillius phase to a pyrochlore structure, accompanied by a crack-free, dense morphology. This structural transition raises the activation energy for charge migration from 0.38 eV to 0.91 eV, reduces leakage current by 1–2 orders of magnitude, and boosts the E b to 5.8 MV/cm at x = 0.5. The linear dielectric pyrochlore phase narrows the P – E loops and lowers the remnant polarization, but at the cost of reduced maximum polarization. A moderate doping level x = 0.3 achieves an optimal balance, delivering a high W rec of 74.2 J/cm 3 and an efficiency of 84% at 4.7 MV/cm, together with excellent frequency, thermal, and cycling stability. This work demonstrates that entropy-regulated Aurivillius-to-pyrochlore structural evolution is an effective strategy for designing high-performance energy-storage ferroelectric thin films.