Engineering heterointerface and composition for ultrathin broadband microwave absorbers based on high entropy oxides/alloys heterostructured composites

Ultrathin and broadband microwave absorption materials are urgently needed for mitigating the detrimental effects of electromagnetic pollution for 5G applications and military stealth. In this work, high entropy heterostructured composites composed of oxides/alloys with abundant heterogeneous interfaces are engineered by introducing in-situ metal conductive phase through high-temperature reduction on solid-phase-sintered high-entropy spinel ferrites (CoNiCuX)Fe2O4. By further tailoring the elemental composition (X=Mn, Zn, Mg, Cr, MnMg, and MnCr), the dielectric, magnetic and conduction properties of the high-entropy heterostructured composites are modulated, resulting in enhanced microwave attenuation ability and optimized impedance matching characteristics. As a result, the (Co0.2Ni0.2Cu0.2Mn0.2Mg0.2)Fe2O4 derived high-entropy oxides (HEOs)/ferroalloy dual-phase composite simultaneously exhibits a minimal reflection loss of -48.77 dB accompanied by a maximum effective absorption bandwidth (EAB) of 6.08 GHz (11.92-18 GHz) at a thickness of only 1.5 mm. Furthermore, an ultra-broadband EAB of 11.5 GHz is realized by constructing macroscale gradient multilayer metamaterials with a thickness of 4.0 mm. This study demonstrates that reasonable composition and heterointerfaces engineering can facilitate synergistic effect of polarization loss, conduction loss and magnetic loss, which enables the heterostructured composites to exhibit superior impedance matching and enhanced microwave loss capability, thus achieving superior microwave absorption performance at thin matching thickness.