Excellent microwave absorption of porous rod spinel by exceeding the Snoek limit via fibrosis and grain refinements

The pure spinel ferrite still cannot exhibit unsatisfactory electromagnetic wave (EMW) absorption performance. In this study, the single‒phase, Co, Ni, and Zn co-doped, porous, defective, nano‒microcrystalline self‒assembled 1D rod‒shaped spinel ferrites were successfully synthesized by coprecipitation combined thermal decomposition method. The sample Co0.5Ni0.2Zn0.3Fe2O4 (C5N2Z3‒C) exhibited excellent EMW absorption performance with a RLmin of ‒65.4 dB at a thickness of 3.2 mm and a EABmax of 7.8 GHz at 2.8 mm. The excellent EMW absorption performance was confirmed to be attributed to its specific microstructure, which precisely regulates the dielectric loss, breaks the Snoek limit and greatly improve the magnetic loss. The EMW dissipation mechanism of the sample C5N2Z3‒C were also surveyed in detail, including optimized impedance matching, multiple reflection and scattering, interfacial polarization and dipole polarization, and multiple natural and exchange resonances. The magnetic properties were controlled by ion doping, the magnetic anisotropy field was regulated by the preparation of porous particles with special morphology, the polarization loss was improved by abundant fine-grained boundaries, heterogeneous interfaces and lattice defects, thus the enhancement of its EMW absorption performance was achieved by multiple regulation.