Magnetic Properties of Fe-Based Amorphous Powder Cores Produced by the Cold-Pressing Method.

Amorphous Fe-Cr-Si-B-C powder cores with glass binders were produced by cold-pressing and sintering at relatively high temperatures below crystallization temperature. The density of the core obtained was about 80%. The magnetic properties of toroidal samples 30 mm in diameter were measured. For the core pressed at 2 GPa, room temperature and sintered at 460°C × 20 min in air, the initial permeability in the frequency range up to 1 MHz for Hm = 5 mOe was about 100, and the core loss at 100 kHz for Bm = 0.1 T was 500 kW/m3. These values were comparable with those of hot-pressed amorphous powder cores, which had been previously reported. Compared with a commercial Sendust powder core widely used for choking coils and fly-back transformers, the initial permeability was approximately equal and the core loss was 30% lower. Furthermore, the domain patterns of the amorphous core were observed and their relation to the magnetic properties was discussed.