Engineering relaxors by entropy for high energy storage performance

Relaxor ferroelectrics are the primary candidates for high-performance energy storage dielectric capacitors. A common approach to tuning the relaxor properties is to regulate the local compositional inhomogeneity, but there is a lack of a quantitative evaluation way for compositional fluctuation in relaxors. Here we propose configurational entropy as an index for the quantitative evaluation of local compositional inhomogeneity. Our results reveal that the local inhomogeneity increases with the entropy via scanning transmission electron microscopy, and relaxor features are accordingly modulated. With the deliberate design of entropy, we achieve an optimal overall energy storage performance in Bi₄Ti₃O₁₂-based medium-entropy films, featuring a high energy density of 178.1 J cm⁻³ with efficiency exceeding 80% and a high figure of merit of 913. By using the medium-entropy films as dielectric layers, we demonstrate a multilayer film capacitor prototype that outperforms conventional multilayer ceramic capacitors.