With the progress of electronic communication technology, the intensity of electromagnetic radiation is getting strength, and the traditional absorbing materials can no longer meet the needs of various current environments. Dielectric nanomaterials have received much attention in energy conversion, electromagnetic shielding and absorption due to their nanosize effects and structural tunable properties. However, the mismatch impedance and the single loss mechanism severely limit its application in the field of microwave absorption. In this paper, we modified the doped ZnCo₂O₄ with the guidance of density functional theory (DFT) simulation, effectively regulate the dielectric parameters and adjust the microwave absorption characteristics, which stems from the transformation of electron energy between doped ions and some defects. Meanwhile, we further experimentally observe significant magnetic components at the doped ZnCo₂O₄, resulting in improved magnetic properties and producing a large number of dipoles. Due to the best impedance match and enhanced polarization loss, the minimum reflection loss is −37 dB, and the effective absorption bandwidth (EAB) is 7.21 GHz. This provides ideas for the design of cobalt acid-based materials as efficient microwave absorbers.

Magnetic/dielectric composite materials with numerous heterointerfaces are highly promising functional materials, which are widely applied in the fields of electromagnetic wave absorption. Constructing heterogeneous structure is beneficial to further enhance the microwave absorption performance of composite materials. However, the process of constructing multi-heterogeneous interfaces is extremely complex. In this work, hollow porous FeCo/Cu/CNTs composite microspheres are prepared by the simple spray drying method and subsequently two-step annealing treatment, which possess abundant heterogeneous interfaces, unique three-dimensional conductive network and magnetic coupling network. This unique structure is beneficial to improving the ability of dielectric loss and magnetic loss, and then achieving an excellent microwave absorption performance. The prepared FeCo/Cu/CNTs-1 composite microspheres maintain a minimum reflection loss (RL) of –48.1 dB and a maximum effective absorption bandwidth of 5.76 GHz at a thickness of 1.8 mm. Generally, this work provides a new idea for designing multi-heterogeneous of microwave absorbing materials.

Development of high-performance microwave absorption materials (MAM) with stabilized magnetic properties at high temperatures is specifically essential but remains challenging. Moreover, the Snoke's limitation restrains the microwave absorption (MA) property of magnetic materials. Modulating alloy components is considered an effective way to solve the aforementioned problems. Herein, a hollow medium-entropy FeCoNiAl alloy with a stable magnetic property is prepared via simple spray-drying and two-step annealing for efficient MA. FeCoNiAl exhibited an ultrabroad effective absorption band (EAB) of 5.84 GHz (12.16–18 GHz) at a thickness of just 1.6 mm, revealing an excellent absorption capability. Furthermore, the MA mechanism of FeCoNiAl is comprehensively investigated via off-axis holography. Finally, the electromagnetic properties, antioxidant properties, and residual magnetism at high temperatures of FeCoNiAl alloys are summarized in detail, providing new insights into the preparation of MAM operating at elevated temperatures.