Preparation and characterization of Fe-SiO₂ soft magnetic composites prepared by classic and modified Stöber Method

Abstract In this study, gas atomized iron powder with the particle size of 10 - 100 μm was coated in two different ways. The coating was created by a chemical procedure, the powder was treated for different periods of time with the classical and modified Stöber process. Toroidal samples were then prepared using different pressures. These samples were heat treated in an argon shielding gas. The complex permeability spectra of the green and heat-treated samples were measured and the effect of pressure, chemical coating time and heat treatment was investigated. The formation of the coatings in each case was confirmed by scanning electron microscopic examinations. Samples with long-term chemical treatment and without heat treatment were appropriate in high-frequency applications (μstat = 50, fFMR = 5 − 15 MHz). After the heat treatment, the relative initial permeability has increased significantly (160-180) and the resonance frequency has decreased (400-4000Hz). Furthermore, it can be stated that a more coherent, thicker coating can be obtained with the modified Stöber method.