Microstructure and magnetic properties of high-density submicron FeBP amorphous soft magnetic composites fabricated via hot pressing

High-density amorphous soft magnetic composites (ASMCs), optimized for operation at MHz frequencies, were fabricated by hot pressing ultrafine, high-iron-content amorphous powders. These submicron FeBP amorphous powders were prepared by chemical reduction, and the effect of sodium hypophosphite (NaH 2 PO 2 ) solution concentration on the morphology, composition, and properties of FeBP amorphous powders was systematically investigated. In the synthesis of amorphous powders, as the concentration of NaH 2 PO 2 solution increases, the particle size of the amorphous powders reduces gradually, reaching a minimum average particle size of 389 nm. When the concentration of NaH 2 PO 2 solution is 1.82 mol/L, the FeBP amorphous powders exhibit the highest iron content among all compositions, approximately 77 at.%. Subsequently, the amorphous powders were employed to fabricate the high-density submicron FeBP amorphous soft magnetic composites through high-temperature and low-pressure processing techniques. The composite exhibits a permeability 17 at 1 MHz and decreases losses through hot pressing at 360 °C. Furthermore, high-temperature hot pressing effectively alleviates internal stress within the magnetic ring structure, eliminating the requirement for annealing treatment. This amorphous FeBP soft magnetic composite exhibits superior permeability in the hundreds of MHz range compared to amorphous powders with similar particle sizes, making it particularly suitable for applications in transformers, sensors, and other fields.