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 Mossbauer 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 -34dB 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 degrees, and a reflection loss peak of more than -10 dB can still be obtained even when the incident angle was 80 degrees. The results show that the easy-plane anisotropy Fe-Si powders with SiO2 coating still possess high microwave absorption performance at oblique incidence.