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

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 [SiW₉O₃₄]^10- as an atomically precise molecular scaffold to sequentially integrate Fe²⁺, Mn²⁺ and Gd³⁺, we programmed a controlled thermal evolution from single-phase FeWO₄ to dual-phase FeWO₄/MnWO₄ and to tri-phase FeWO₄/MnWO₄/Gd₂W₂O₉ 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 FeWO₄/MnWO₄ interface boosts interfacial polarization, elevating the minimum reflection loss (RL_min) from -42.95 dB to -60.39 dB. Subsequent introduction of Gd³⁺ induces a distinct Gd₂W₂O₉ 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.