Strategic grain boundary diffusion process for high-performance Ce-containing sintered Nd-Fe-B magnets

Sintered Nd-Fe-B magnets are an important driver of green technology, and the grain boundary diffusion process (GBDP) has become the most economically efficient method to improve the overall magnetic properties of sintered Nd-Fe-B magnets. In the work, to further reduce the utilization cost of sintered Nd-Fe-B permanent magnets with high performance, the strategic GBDP was explored based on the demagnetization characteristics of Nd-Fe-B permanent magnet materials in motors. The peculiar fact about the process was that the diffusion source was deposited on a part of the c-plane, that is, the strategic selected area grain boundary diffusion process (SSAGBDP). With the objective of addressing the edge demagnetization, the diffusion source was initially deposited only at the edges of the c-plane. Despite the overall magnetic properties and temperature coefficients of the diffused magnet were significantly enhanced, the serious deteriorations of squareness and surface magnetic field were particularly worrying. Consequently, the central area of the magnet was simultaneously strengthened. The squareness and demagnetization property of the magnet after S-SAGBDP were greatly improved, and the amount of heavy rare earths was reduced by 25%. The above work clearly illustrates the practical value of S-SAGBDP, which is helpful to develop the cost-effective and commercial-grade sintered Nd-Fe-B magnets.