Microwave absorption properties of easy-plane anisotropy Fe–Si powders with surface modification in the frequency range of 0.1–4 GHz

To satisfy impedance matching at low frequencies and obtain high microwave absorption performance, easy-plane anisotropy Fe–Si powders coated with SiO₂ were produced by a ball milling technique and a chemical deposition method. Then, a scanning electron microscope, a transmission electron microscope, an X-ray photoelectron spectrometer, an X-ray diffractometer, a Mössbauer spectrometer, a vibrating sample magnetometer, and a vector network analyzer were used to characterize the samples. Compared to easy-plane anisotropy Fe–Si powders without surface modification, the dielectric constant of easy-plane anisotropy Fe–Si powders with SiO₂ coating decreased dramatically and the microwave absorption performance was improved significantly. The reflection loss peak reached − 10 dB when the thickness was 1.4 mm and even reached − 34 dB when the thickness was 4.5 mm, exhibiting great potential for application in thin absorbers working in the frequency range of 0.1–4 GHz. In addition, the microwave absorption performance at oblique incidence was also investigated. A reflection loss peak of − 30 dB was obtained when the incident angle was 30°, and a reflection loss peak of more than − 10 dB can still be obtained even when the incident angle was 80°. The results show that the easy-plane anisotropy Fe–Si powders with SiO₂ coating still possess high microwave absorption performance at oblique incidence.