Stepwise Construction of Multi‐Phase Heterointerfaces for Dielectric Decoupling and Enhanced Microwave Absorption

ABSTRACT High‐performance dielectric microwave absorbing materials (MAMs) face a persistent trade‐off between impedance matching and attenuation due to the inherent coupling of real ( ε ′) and imaginary ( ε ″) permittivity. Herein, a sequential interface engineering (SIE) strategy is proposed to achieve dielectric decoupling by stepwise constructing multi‐phase heterointerfaces on reduced graphene oxide. Using a lacunary polyoxometalate [SiW 9 O 34 ] 10− as an atomically precise molecular scaffold to sequentially integrate Fe 2+ , Mn 2+ and Gd 3+ , we programmed a controlled thermal evolution from single‐phase FeWO 4 to dual‐phase FeWO 4 /MnWO 4 and to tri‐phase FeWO 4 /MnWO 4 /Gd 2 W 2 O 9 heterostructures. This “interface‐by‐interface” assembly allows for a stable ε ′ baseline maintained by the tungsten‐oxygen system, while ε ″ is independently enhanced by the increasing density of heterojunctions. Specifically, the FeWO 4 /MnWO 4 interface boosts interfacial polarization, elevating the minimum reflection loss (RL min ) from −42.95 dB to −60.39 dB. Subsequent introduction of Gd 3+ induces a distinct Gd 2 W 2 O 9 phase that diversifies polarization relaxation pathways, significantly broadening effective absorption bandwidth (EAB) from 6.08 to 8.24 GHz with a further improved RL min to ‐62.43 dB. Density functional theory calculations confirm substantial interfacial charge transfer and built‐in electric fields at each stage. This work establishes a rational “molecular‐to‐nano” paradigm for precision heterostructure design, offering a versatile blueprint for programming interfacial electronic environments for functional materials.