The percolation effect and optimization of soft magnetic properties of FeSiAl magnetic powder cores

Abstract In this paper, a new magnetic percolation phenomenon between the green compact density ρ and effective permeability μe in FeSi 9.6 Al 6.5 magnetic powder cores, was discovered. The Magnetic Percolation Area of ρ is the range of 5.6 g/cm 3  ∼ 5.78 g/cm 3 , and the percolation threshold is 5.78 g/cm 3 . As a result of the guidance of the percolation theory, the best comprehensive magnetic properties have been optimized through adjusting the distribution of powders. The special distribution of the magnetic powder cores with the best comprehensive magnetic properties was as follows: the content 60% with the particle size distribution of 100–200 mesh, the content 20% with the particle size distribution of 200–325 mesh and the content 20% with the particle size distribution of ≥400 mesh. When the green compact density ρ of cores was 5.79 g/cm 3 , and the frequency was in the range of 1 kHz ∼ 100 kHz, the best comprehensive magnetic properties were as follows: μe = 91, ∆μ = 0.61%, μe(H80 Oe) = 43, μe(H100 Oe) = 33, μe(H120 Oe) = 26, Pc(50 mT/20 kHz) = 30.58 kW/m 3 , Pc(50 mT/50 kHz) = 76.85 kW/m 3 , Pc(50 mT/100 kHz) = 178 kW/m 3 . Not only have those cores the excellent constant magnetic properties with frequency, the excellent DC superposition characteristic and the lower loss at high frequency, but also the effective permeability outstandingly goes up, which has important significance for the miniaturization of inductance components.