Lattice Engineering for Enhancing Electromagnetic Wave Absorption Performance of Mn-Doped Ni5Co3Fe2 Medium-Entropy Alloy Aerogels.

Medium-entropy alloys (MEAs) are promising electromagnetic wave absorption (EMA) materials for their designable crystal structures, tunable electromagnetic properties, and stable phase structures and so on. However, their inherent high density and excessive dielectric constant cause severe impedance mismatch, which greatly limits practical applications. Herein, we propose a lattice distortion engineering strategy via Mn doping, combined with a template-free self-propagating combustion method, to construct lightweight Ni5Co3Fe2 MEA aerogels with synergistically optimized impedance matching and electromagnetic energy dissipation. TEM and GPA confirm that Mn doping induces significant lattice distortion in the optimal (Ni5Co3Fe2)0.8Mn0.2 aerogel. The Mn-induced lattice distortion precisely dual-regulates electromagnetic properties, tailoring electrical conductivity to optimize impedance matching and introducing abundant defective dipoles to boost polarization loss. Its three-dimensional interconnected porous structure delivers an ultralow density of 0.0376 g cm-3, supporting preliminary lightweight impedance matching optimization. This synergistic design endows the aerogel with an exceptional RLmin of -82.9 dB at 1.43 mm and 4.42 GHz EAB, outperforming state-of-the-art MEA absorbers and providing a new lattice distortion engineering paradigm for lightweight high-efficiency EMA materials.