Influence of shape and chemical and phase compositions of iron-containing particles on microwave performance of composites with an insulating matrix

The structure and microwave magnetic properties of Fe powders grounded in argon or acetone and also of Fe-Si-C and amorphous Fe-Co-Si-C powders mechanically alloyed in argon are studied using X-ray diffraction, Mossbauer spectroscopy, granulometric and microscopic analyses, magnetostatic measurements, and microwave spectroscopy. The goal of investigation is to determine the influence of factors (shape, size, and chemical and phase compositions of grains) governing the microwave material parameters of composites based on these alloys in the frequency range 0.1-3.0 GHz. It is shown that the difference in the grain shape is the basic reason for the difference in the microwave permeability at low frequencies (3 GHz or lower). At higher frequencies, the magnetic properties are related to the skin effect and depend largely on the grain size. The differences in the microwave properties of the composites are not significant and are concealed by the above effects.