High-entropy porous spinel ferrite @ amorphous carbon nanocomposites with abundant structural defects for wide-band electromagnetic wave absorption

The design of defects and microstructures is a key strategy for optimizing electromagnetic wave (EMW) absorption abilities of high-entropy oxides (HEOs). However, the traditional design strategies remain significant challenges in terms of achieving broadband absorption. Herein, a series of carbon-coated HEOs with foam-like porous structures were successfully prepared. By simply adjusting the concentration ratio of the metal ions, the frequency corresponding to the absorption peak can be controllable. This enables to precisely tune the bandwidth range of the HEOs@C, resulting in excellent EMW absorption performance (minimum reflection loss: -67.68 dB, effective absorption bandwidth: 10.51 GHz), which far exceeds most of the materials yet reported. The experimental results indicate that the regulation of entropy configuration can generate significant grain boundaries, dense distorted lattice and abundant oxygen defects. The various polarization losses caused by these characteristics combined with excellent magnetic loss provided by HEOs core, results in the excellent EMW attenuation performance. The strategy for regulating electromagnetic performance through entropy engineering can be expanded to other materials, which could facilitate the development of emerging EMW absorbers.