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.