Engineering Crystallinity Gradient via Layer‐by‐Layer Annealing to Boost Energy Storage Performance of PLZT Thin Films

ABSTRACT Functional gradient materials are materials in which composition or microstructure varies spatially to achieve synergistic property optimization. In this letter, a multilayer thin film with a designed crystallinity gradient is constructed solely using (Pb, La)(Zr 0.52 Ti 0.48 )O 3 via layer‐by‐layer annealing. This approach integrates distinct crystallinity levels within individual layers to leverage their complementary properties, where high‐crystallinity layers enhance polarization and low‐crystallinity layers improve breakdown strength. Consequently, the energy storage performance surpasses that of single‐layer films. The optimized bilayer (2L) structure achieves a recoverable energy density ( W rec ) of 90.1 J/cm 3 at 6.00 MV/cm, attributed to the synergistic enhancement of the breakdown field and polarization (40 µC/cm 2 ). This layer‐by‐layer annealing strategy offers a promisingly extendable approach for engineering crystallinity gradients in various functional thin films.