Properties of high-density magnetic composite fabricated from iron powder coated with a new type phosphate insulator

We have developed a new powder magnetic core, named the high-density magnetic composite (HDMC), with high density, high magnetic flux density, and high strength. However, the HDMC, which was fabricated from iron powder coated with a phosphate amorphous insulator, has large eddy-current loss under high frequency because the resistivity was small (<10 μΩ·m). To solve the deficiency, a new type of phosphate amorphous insulator was developed. The phosphate amorphous insulator with Sr²⁺ or Y³⁺ was found to have high resistivity above 50 μΩ·m in keeping the high magnetic flux density and strength of the HDMC. The HDMC, whose starting material was iron powder coated with a strontium phosphate amorphous insulator, compacted at 1176 MPa with heat treatment at 673 K and had properties as follows: d=7.70 Mg/m³, μ_m=610,B_5k=1.51 T B_10k=1.71 T, _bH_c=300 A/m, resistivity=100 μΩ·m, TRS=180 MP, iron loss (B_max=1 T,f=400 Hz)=400 kW/m³.