Influence of Si/Cr Ratio on Flake Morphology and Magnetic Properties of Fe-Si-Al-Cr Particles

Fe-Si-Al-Cr flaky particles, as soft magnetic materials with high microwave permeability, can be used for microwave absorption. In order to enhance the permeability of the materials, some Si atoms were replaced by Cr atoms. Fe₇₅Si_15-xAl₁₀Cr_x (x = 0, 2, 4, 6, 8) flake-shaped particles were prepared by crushing ingots by ball milling. X-ray diffraction shows that the phase of all alloys is that of a α-Fe matrix. Scanning electron microscopy shows that the particles were transformed into a flaky shape, and the average aspect ratio (width/thickness) increased with x. The mean diameters of the flaky particles increased from 31.1 μm to 230 μm. Mössbauer spectroscopy shows that the peak intensity ratio of I_2,5/I_3,4 of a sextet increases from 2.90 to 3.3 when x increases from 0 to 6, since Fe-Si-Al-Cr flaky particles have a stronger tendency to possess a planar anisotropy than Fe-Si-Al particles, which increases magnetic permeability. Saturation magnetization (M_s) of the particles increased from 127 emu/g to 144 emu/g with x increasing from 0 to 2, but there is no significant change of M_s when x increases from 2 to 6. The microwave permeability dispersion spectra were measured in the frequency range between 0.5 and 8 GHz. Thus, high permeability of Fe-Si-Al-Cr alloys can be obtained when some Si atoms are replaced by Cr atoms, which leads to a change of planar anisotropy and M_s.