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.