Effect of iron particle size and volume fraction on the magnetic properties of Fe/silicate glass soft magnetic composites

•A new soft magnetic composite (SMC) material design scheme was put forward, for increasing annealing temperature and reducing thermal mismatch stress.•SMC with silicate glass insulation layers was prepared based on our design scheme.•Comparing with other SMCs, annealing temperature was higher, holding time was longer (700 °C for 90 min).•The composite has higher performance than conventional composite. Its relative permeability μm, Bs and Br and Hc were 622, 1.57 T, 1.43 T, 278 A/m, respectively.

Fe/silicate glass soft magnetic composites (SMC) were fabricated by powder metallurgy with 1000 MPa pressure at room temperature, and then annealed at 700 °C for 90 min. The iron particles distributed uniformly in the composites, and have been separated from each other by a continuous silicate glass insulating layer. Fe/glass interface was well bonded and a quasi-continuous layer Fe3O4 and FeO exited. Very fine crystalline phases Na12Ca3Fe2(Si6O18)2 were formed in silicate glass. Composite containing 57 vol% 75 μm iron particles demonstrated highest resistivity of 7.8×10−3 Ω m. The μm, Bs and Bt increased while Hc of Fe/silicate glass composites decreased with the increase of average size of iron particles. The composite with highest amount (82 vol%) and largest average size (140 μm) of iron particles demonstrated best μm, Bs and Bt and Hc, which were 622, 1.57 T, 1.43 T, 278 A/m, respectively. The composite containing 57 vol% 75 μm iron particles demonstrated minimum core loss of 3.5 W/kg at 50 Hz and 28.1 W/kg at 400 Hz, while the composite containing 82 vol% 140 μm iron particles exhibited maximum core loss of 5.2 W/kg at 50 Hz and 67.7 W/kg at 400 Hz.