Entropy‐Driven Phase Engineering of Carbon Confined Alloy Composites Accompanied by Lattice Distortion and Point Defects for High‐Efficiency Electromagnetic Wave Absorption

ABSTRACT

Uncovering the structural‐functional relationship between entropy‐driven phase structures and lattice distortion/points defect‐induced dielectric polarization has always been a long‐standing challenge in electromagnetic (EM) wave absorption field. In this work, a strategy of entropy‐driven phase engineering was proposed to regulate the evolution of EM spectra of carbon confined alloy composites. With increasing alloy entropy, the phase structure evolves from a single FCC phase to an FCC+BCC dual‐phase structure, accompanied by lattice distortion and point defects. These entropy‐induced effects effectively enhance electron scattering, moderately suppress excessive electrical conductivity, and weaken the skin effect, thereby significantly improving impedance matching. Moreover, abundant dual‐phase interfaces and lattice defects generate strong interfacial polarization and dipole polarization, which further boost dielectric loss. Importantly, polarization‐dominant medium‐entropy FeCoNiCu@C has been obtained by balancing the contribution between dielectric loss and impedance matching, as well as polarization loss and conduction loss, which realizes a broad effective absorption bandwidth (EAB) of 5.8 GHz at 1.8 mm and a minimum reflection loss ( RL ) of −42.19 dB at 3.85 mm. This work demonstrates that entropy‐driven phase engineering accompanied by lattice distortion and point defects provides an effective strategy to synergistically regulate the evolution of EM spectra, thus achieving high‐efficiency EM wave absorption performance.