Spark plasma sintering and diffusion technology yield high-performance permanent magnets for green industries

A research team has developed an innovative manufacturing process for permanent magnets that overcomes the limitations of conventional techniques. The team’s breakthrough significantly advances the diffusion technology, which is essential for improving magnetic performance, and creates new possibilities for applying high-efficiency magnets in eco-friendly industries such as electric vehicles, wind turbines, and robotics.

The findings are published in the Journal of Alloys and Compounds.

The joint research team from the Nano Technology Research Division at DGIST was led by Dr. Donghwan Kim and Dr. Jungmin Kim.

With the rapid growth of the electric vehicle and wind power sectors, the demand for powerful permanent magnets capable of stable operation at high temperatures has soared. A major example is the neodymium (Nd-Fe-B) permanent magnet, widely used in electric vehicle motors. However, these magnets experience a decline in magnetic performance under extreme heat, requiring the addition of heavy rare-earth elements such as terbium (Tb) and dysprosium (Dy) to maintain their strength. The challenge is that these elements are both rare and expensive.

To address this issue, the grain boundary diffusion process has been widely adopted. This technique enhances magnetic performance by infiltrating a small amount of heavy rare-earth material into the magnet’s surface. However, diffusion in this process is limited to the surface layer and does not penetrate into the magnet’s interior, making it difficult to apply to thick magnets.

To overcome this limitation, the research team combined spark plasma sintering, an advanced manufacturing technique, with the grain boundary diffusion process. By pre-mixing the diffusion material during the powder-based magnet fabrication stage, uniform diffusion was achieved throughout the magnet. Consequently, the diffusion depth increased markedly compared with that achieved by existing methods, allowing for the creation of a core–shell structure in which the magnet exhibits uniform and enhanced magnetic performance.

Remarkably, even with the same amount of rare-earth material, the new process achieved higher diffusion efficiency and significantly improved overall performance. This advancement makes it possible to produce magnets that are smaller and lighter while maintaining strong magnetic strength. It is expected to contribute to the miniaturization, weight reduction, and improved energy efficiency of electric vehicle motors. Additionally, the process shows great potential for application to large-scale magnets.

Principal Researcher Dr. Donghwan Kim stated, “This study presents a method that overcomes the limitations of the conventional grain boundary diffusion technology, enabling uniform performance throughout the magnet. It will make a significant contribution to the development of high-performance permanent magnets required in eco-friendly energy industries such as electric vehicles and wind power generation.”