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 /spl mu//spl Omega//spl middot/m). To solve the deficiency, a new type of phosphate amorphous insulator was developed. The phosphate amorphous insulator with Sr/sup 2+/ or Y/sup 3+/ was found to have high resistivity above 50 /spl mu//spl Omega//spl middot/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/m/sup 3/, /spl mu//sub m/=610,B/sub 5k/=1.51 T B/sub 10k/=1.71 T, /sub b/H/sub c/=300 A/m, resistivity=100 /spl mu//spl Omega//spl middot/m, TRS=180 MP, iron loss (B/sub max/=1 T,f=400 Hz)=400 kW/m/sup 3/.