Production and properties of soft magnetic cores made from Fe-rich FeSiBPCu powders

Fe-rich Fe_83.3Si₄B₈P₄Cu_0.7 powders with the particle sizes below 150μ m were prepared by spinning water atomization process. As-prepared powders were structurally amorphous. The powders with small and large particle size were insulated with the phenol resin and compacted to a toroidal shaped core (outer diameter ∼ 13 , inner diameter ∼ 8 , and height ∼ 5-6 mm) by cold-pressing at the pressure of ∼ 0.5-1.5 GPa. Core loss decreases, and magnetic permeability increases after annealing treatment at 350 °C for 20 min. The powder particles in the annealed core consist of nanocrystalline α-Fe grains in the amorphous matrix. Cores exhibit a constant initial permeability (μ_i) up to the frequency range of ∼ 30 MHz. Core loss is shown to be dependent on particle size. Cores made from smaller powder particles have low core loss at high frequencies. Our powder cores exhibit lower core loss than the Somaloy500 powder cores measured under the magnetic induction of 0.5 T, and are promising for filling the gaps in high frequency and high induction application of ferrite materials.