Microstructure induced dielectric loss in lightweight Fe₃O₄ foam for electromagnetic wave absorption

Fe₃O₄ has been extensively applied in electromagnetic wave absorption field profiting from its advantageous magnetic loss, low cost and environmental benignity. Nevertheless, the inherent drawbacks of high density, low permittivity and easily magnetic aggregation are still the obstacles for pristine Fe₃O₄ becoming ideal absorbents. To overcome such limitations, a design mentality of constructing 3D structure shaped by curled 2D porous surface is proposed in this study. 3D structure overcomes the easy-agglomeration issue of 2D materials and meanwhile maintains their conductivity. The complex permittivity of samples is regulated by adjusting the microstructure of Fe₃O₄ to achieve optimum impedance matching. Defect induced polarization and interfacial polarization are the main loss mechanisms. Impressively, the density of S0.5 is only 0.05078 g/cm³ and the effective absorption bandwidth is up to 6.24 GHz (11.76-18 GHz) at 1.8 mm. This work provided a new insight for structurally improving the EMW absorption performance of pure magnetic materials.