All-in-one: Multi-parameter engineering on γ-Fe2O3 for ultra-broadband microwave absorption

The functionality and property of materials are normally controlled by changing their composition, defects, morphology, lattice, crystallinity, etc. However, achieving a wide effective absorption bandwidth through multiple-parameter optimization is less reported. Simultaneously adjusting these parameters can serve as an effective control knob to increase dielectric loss, including conduction and polarization, thereby providing a broadband absorption toward radiated microwave for potential applications. Herein, magnetic γ-Fe2O3 in a two-dimensional configuration was synthesized through a molten salt process, which was further modified by Co and Al heteroatoms to facilitate more polarization processes. The reinforcement of conduction loss is achieved by increasing the crystallinity of the absorber, which facilitates the rapid transfer of free electrons and reduces scattering. Controlled alkaline etching was employed to extract a portion of the intercalated Al atoms. Henceforth, appropriate lattice distortion and numerous O vacancies are constructed, which can not only generate new polarization centers on the absorber matrix but also maintain a high crystalline structure with good conduction loss feature. In addition, the magnetic loss and impedance matching characters are optimized. As a result, the composition, structure, defects, and crystallinity of magnetic γ-Fe2O3 nanosheets have all been optimized, which enable an impressive microwave absorption performance with an effective absorption bandwidth of 7.82 GHz and a minimum reflection loss of −54.9 dB. This work explores improving the electromagnetic parameters of absorbers through collaborative regulation of multiple parameters and provides guidance for a novel and facile strategy for controlling microwave absorbers.