Effect of Rare-Earth Content on Coercivity and Temperature Stability of Sintered Nd-Fe-B Magnets Prepared by Dual-Alloy Method

The influence of rare earth content on coercivity and temperature stability with dual-alloy method has been investigated. It is found that the coercivity of magnets increases rapidly firstly and then slightly with the increasing of rare earth content from the range of 29.5 wt% to 33.5 wt%. The coercivity and the temperature coefficient of coercivity will get better with rare earth content of 31.5 wt%. The result of magnetic anisotropy field of magnet revealed that it almost has no change with different rare-earth content. Scanning electron microscopy (SEM) and Transmission electron microscope (TEM) revealed that continuous thin layers of Nd-rich phase about 4 nm were found along the grain boundaries in the annealed sample at 31.5 wt% rare earth content, while the grain boundary width of magnet exceeds 8 nm at 33.5 wt%.