Quasi‐Parallel Ferroelectric Composites Decoupling the Permittivity‐Tunability Trade‐Off

The development of frequency‐agile devices is constrained by the permittivity–tunability trade‐off in ferroelectric materials, where high tunability is typically accompanied by excessive permittivity and dielectric loss. Conventional ceramic/polymer composites can alleviate impedance mismatch but suffer from severe tunability degradation due to depolarization effects. Here, we report a quasi‐parallel ferroelectric composite that enables improved decoupling between permittivity, loss, and tunability. This is achieved via a cross‐scale dual‐correction strategy, where fine sol–gel‐derived Bi 6 Ti 5 WO 22 particles enhance wall densification while controlled freezing reduces structural defects and improves alignment. Furthermore, real‐structure finite‐element modeling demonstrates that mitigating these microstructural deviations is essential for maximizing local electric field utilization. The resulting 15 vol. % composite exhibits a high dielectric tunability of 50% at 30 kV cm −1 , retaining ∼ 83% of the bulk ceramic tunability, together with an ultralow dielectric loss (tan δ < 0.001) at room temperature. A high figure of merit (FOM) of 633 is achieved at a permittivity more favorable for impedance matching than that of conventional ferroelectric ceramics. These results demonstrate that cross‐scale structural and material optimization provides an effective strategy for high‐performance tunable dielectric composites.