Abstract: single-phase anti-perovskite medium-entropy alloy nitride foams (MEANFs), as innovative materials for electromagnetic wave (EMW) absorption, have been successfully synthesized through the lattice expansion induced by nitrogen doping. This achievement notably overcomes the inherent constraints of conventional metal-based absorbers, including low resonance frequency, high conductivity, and elevated density, for the synergistic advantages provided by multimetallic alloys and foams. Microstructural analysis with comprehensive theoretical calculations provides in-depth insights into the formation mechanism, electronic structure, and magnetic moment of MEANFs. Furthermore, deliberate component design along with the foam structure proves to be an effective strategy for enhancing impedance matching and absorption. The results show that the MEANFs exhibit a minimum reflection loss (RL_min) value of -60.32 dB and a maximum effective absorption bandwidth (EAB_max) of 5.28 GHz at 1.69 mm. This augmentation of energy dissipation in EMW is predominantly attributed to factors such as porous structure, interfacial polarization, defect-induced polarization, and magnetic resonance. This study demonstrates a facile and efficient approach for synthesizing single-phase medium-entropy alloys, emphasizing their potential as materials for electromagnetic wave absorption due to their adjustable magnetic-dielectric properties.

Key words: Medium-entropy alloy nitride foams, Anti-perovskite structure, Lattice expansion Engineering, Magnetic-dielectric synergistic, Electromagnetic wave absorption