Multilayered core–shell high-entropy alloy@Air@La_0.8Ca_0.2CoO₃ microsphere: a magnetic loss-dominated electromagnetic wave absorber

High-entropy alloy (HEA)@Air@La_0.8Ca_0.2CoO₃ multilayered core–shell microsphere has been synthesized as an electromagnetic wave (EMW) absorber. The synthesis was performed by a two-step hydrothermal–calcination method, and the calcination process was changed (350 °C, 450 °C, 650 °C and 800 °C). For morphology analysis, multilayered structure was achieved. Both surface morphology and crystalline phase were changed with the variation of calcination temperature. For EMW absorption properties, it was mainly dominated by magnetic loss in such absorbers. When the calcination temperatures were 350 °C and 450 °C, decent complex permeability was gained. The minimum reflection loss (RL_min) was achieved when the calcination temperature was 450 °C, reaching up to − 46.5 dB at the matching thickness of 3.7 mm. Such great EMW absorption efficiency was assisted by good impedance matching between absorber and air and was mainly dominated by attentively design of component and structure, which leads to natural/exchange resonance, eddy current loss, interfacial polarization, multiple reflections/scatterings, etc. Such absorber paves the way for further design of EMW attenuation materials and has great potential for application and scientific research.