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

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 μ_m, B_s and B_t increased while H_c 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 μ_m, B_s and B_t and H_c, 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.