Effect of reduction-diffusion time on microstructure and properties of Nd-Fe-B nanoparticles prepared by low-energy chemical method

Nd-Fe-B nanoparticles have been successfully prepared by using an optimized low-energy chemical method. The effects of reduction-diffusion time on the microstructure and properties of Nd-Fe-B nanoparticles were investigated by using TEM, XRD, SEM, VSM and Rietveld calculations. The results showed that when the reduction-diffusion time was short, the reaction was not sufficient, which resulted in a residual H5Nd2 phase. When the reduction-diffusion time was prolonged, the H5Nd2 phase gradually decreased and the relative crystallinity of Nd2Fe14B phase gradually increased. Moreover, the grain size grew and the rich Nd phase appeared gradually around the grains. Furthermore, as the reduction-diffusion time was prolonged, the coercive force of Nd-Fe-B nanoparticles increased first and then decreased. When the holding time was extended to 180 min, the coercive force reached a maximum of about 4.85 kOe and the magnetic energy product was about 2.5 MGOe.