High-entropy engineering of A-site in MAX phases toward superior microwave absorption properties

The increasing electromagnetic pollution necessitates the development of advanced microwave absorbers. Although MAX phases exhibit chemical stability and electrical conductivity, their absorption performance is limited by a singular loss mechanism. Here, we propose a “pre-placed vacancy and isomorphous occupancy” strategy to engineer A-site high-entropy (HE) MAX phases, achieving unprecedented incorporation of large-radius elements (Ag and Bi). The optimized absorber delivers exceptional microwave absorption performance, with a minimum reflection loss of −71.6 dB (at 3.05 mm) and a broad effective absorption bandwidth of 4.1 GHz (at just 1.25 mm), outperforming both reported MAX phase variants and commercial absorbers. These remarkable properties stem from three synergistic mechanisms: A-site composition tailoring optimized impedance matching, HE-induced lattice distortion enhanced dipolar polarization, and A-site entropy engineering increased conduction loss. Our work pioneers a novel method for manipulating electromagnetic response in MAX phases through atomic-scale entropy engineering, paving the way for next-generation electromagnetic protection materials.