Ni-Zn 18H ferrite materials with abundant structural defects for waveband-tunable electromagnetic wave absorption

The design of defects and microstructures plays a crucial role in optimizing the electromagnetic wave (EMW) absorption performance of ferrites. However, the limited loss characteristics and simple phase structure of conventional ferrites severely hinder their further development. In this study, a series of Ni-Zn 18H hexaferrites were successfully synthesized by solid-state reaction method, and precise compositional optimization was carried out. By adjusting the concentration ratio of Ni and Zn metal ions, the effective absorption bandwidth (C to Ku band) of reflection loss can be adjusted. Notably, the Ni-Zn 18H hexaferrite with x  = 1 achieved an optimal reflection loss of −33.33 dB at 6.53 GHz, with a matching thickness of 5.5 mm, and its effective absorption bandwidth extended to 2 GHz. The experimental results indicate that compositional modulation can cause substantial lattice distortion and oxygen vacancies, thereby enhancing defect-induced polarization and improving the magnetic loss performance of the material. Consequently, these structural defects contribute to achieving excellent tunable EMW absorption performance. This study, therefore, provides valuable insights into the development of waveband-tunable EMW absorbers through defect engineering.