Research Progress of Sintered Nd-Fe-B Permanent Magnets With High Coercivity

Sintered Nd-Fe-B rare earth permanent magnets have excellent magnetic properties. But its Curie temperature is low, which makes it limited in the field of high temperature applications. With the rapid development of new energy vehicles, wind power and other emerging industries, the market demand for high temperature sintered Nd-Fe-B magnets have been greatly raised. Therefore, in order to improve the service temperature of Nd-Fe-B material, new technologies have been developed to increase the coercivity of sintered Nd-Fe-B magnets. At the same time, the investigation on the high coercivity sintered Nd-Fe-B magnets with low Dy content or without Dy content become the highlights in order toreduce the product cost and consumption of heavy rare earth metals. It is found that the coercivity of Nd-Fe-B magnets can be improved to a certain extent by refined grain technology, grain boundary diffusion technology and grain boundary doping technology. In this paper, the latest research progress of these three new technologies are reviewed.