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

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.