Design of morphology-controlled cobalt-based spinel oxides for efficient X-band microwave absorption

The cobalt-based spinel structure oxides with synergistic effect of magnetic loss and dielectric loss have important applications in electromagnetic wave absorption. And the excess 0.5 oxygen atoms in MnCo2O4.5 provide more vacancies than traditional MnCo2O4 spinel structure and improve the electrical conductivity. In the current study, MnCo2O4.5 microsphere clusters, MnCo2O4.5 microcubic spheres and MnCo2O4.5 flowery spheres were prepared by solvothermal method and annealing process. Among the final samples with different morphologies, MnCo2O4.5 microcubic spheres showed outstanding microwave absorption capabilities, with a minimum reflection loss (RLmin) of -51.52 dB at 2.2 mm. When the thickness was further increased to 2.3 mm, the effective absorption bandwidth could be as wide as 5.36 GHz, covering most of the X-band. The excellent absorption performance of electromagnetic waves is related to the modulability of the complex dielectric parameters, the optimization of impedance matching, and the enhancement of the polarization relaxation process through the improvement of the morphologies. This work provides guidance and support for refining the electromagnetic wave absorption potential of cobalt-based spinel oxides and for designing highly efficient electromagnetic wave absorbers in the X-band.