Influence of annealing treatment on microstructure and soft magnetic properties of Fe-B-P nanoparticles prepared by aqueous chemical reduction

Fe-B-P amorphous nanoparticles prepared by aqueous chemical reduction were annealed at 300 °C ∼ 500 °C for 30 min. The microstructure and the soft magnetic properties of the specimens were investigated by X-ray diffraction, Mossbauer spectroscopy, scanning electron microscopy and vibrating sample magnetometry, etc.. The results show that the particles are monodisperse Fe-B-P amorphous nanoparticles and the grain diameter distribution is from 200 to 300 nm with a very narrow size distribution. About 3 % of α-Fe appeared in the amorphous particles after annealing treatment at 300 °C for 30 min. After an annealing treatment at 400 °C and 500 °C for 30 min the samples are completely crystallized. The crystallization phases are α-Fe, Fe2B and Fe3B. The soft magnetism after 300 °C annealing treatment is better than other specimens, while the full crystallization deteriorates the soft magnetic performance of the specimens after annealing at 400 °C and 500 °C.