Magnetic properties and power losses of inorganic, organic and hybrid-based soft magnetic composites

Fe-3Si gas atomised powder is coated with iron phosphate, epoxy resin and a hybrid of the two coatings to produce soft magnetic composites (SMCs). Consolidation of iron phosphate powders is performed by uniaxial compaction and field assisted sintering technology (FAST), whereas resin and hybrid coating are compaction by uniaxial compaction followed by curing. This study shows that the optimisation of the physical and magnetic properties of FAST-consolidated iron phosphate SMCs strongly depends on the coating thickness and the FAST cycle performed. Compact density, electrical resistivity, magnetic properties and power losses are discussed in terms of the type of coating and consolidation method. Overall, FAST consolidation results in lower coercivity and higher densification than cold pressing, producing higher saturation magnetisation and permeability. However, lower power losses ( P) are obtained with the cold-pressed SMCs ( P = 9040 mW/cm 3 at f = 1 MHz and B = 50 mT). In addition, the high ductility of the resin coating leads to a very thin layer between the Fe-3Si particles, thus maximising the permeability (μ’ = 65). By contrast, the highest electrical resistivity (∼10 7 μΩ cm) is obtained with the hybrid SMC due to the good coupling between the two coatings.