Quantitative Evaluation of Loss Capability for In Situ Conductive Phase Enhanced Microwave Absorption of High‐Entropy Transition Metal Oxides

Abstract High‐entropy oxides (HEO) with high stability and designability are potential microwave absorbers that serve in harsh environments. However, loss design is critical for the absorption performance of HEO due to its weak intrinsic loss capability. Inadequate loss ability results in considerable secondary reflection. Here, an in situ conductive heterogeneous phase is constructed in (Fe 0.2x Co 0.2 Ni 0.2 Cr 0.2 Mn 0.2 ) 3 O 4 ( x = 1–5) using a reductive circumstance, to form a dual‐phase composite. Both the ohmic and dielectric loss are enhanced as the conductive phase is introduced, while great impedance matching condition is well maintained. Hence, the composites can achieve substantial absorption across the whole X or Ku band with a thin thickness. Furthermore, key efforts are made to reveal the relationship between the absorbing performance and loss capability of an absorber. The analytical expression of the theoretical threshold of attenuation constant is derived. Based on the statistics of experimental data, the broad feasibility and practicability of the proposed theoretical threshold of attenuation constant are confirmed and discussed. Combined with both the theoretical and experimental studies, the mechanism by which the conductive phase contributes to increased absorption is also disclosed, providing an effective basis for the loss design of broadband microwave absorbers.