Scientists develop high-performance permanent magnet without expensive heavy rare earth elements

The Nano Materials Research Division at the Korea Institute of Materials Science (KIMS), led by Dr. Tae-Hoon Kim and Dr. Jung-Goo Lee has successfully developed a grain boundary diffusion process that enables the fabrication of high-performance permanent magnets without the use of expensive heavy rare earth elements. This pioneering technology marks the world’s first achievement in this field.

The findings are published in Acta Materialia.

Permanent magnets are key components in various high-value-added products, including electric vehicle (EV) motors and robots. However, conventional permanent magnet manufacturing processes have been heavily dependent on heavy rare earth elements, which are exclusively produced by China, leading to high resource dependency and production costs.

To overcome these limitations, the research team successfully developed a high-end, high-performance permanent magnet without the use of expensive heavy rare earth elements. The core of this breakthrough technology lies in its two-step grain boundary diffusion process.

The grain boundary diffusion process is a key technology designed to enhance the performance of permanent magnets. In this process, the heavy rare-earth materials are coated to the surface of the magnet, followed by high-temperature heat treatment.

During the heat-treatment, the heavy rare-earths diffuse into the magnet’s interior along the grain boundaries, improving the coercivity—the ability of the magnet to retain its magnetization.

The two-step grain boundary diffusion process developed by the research team involves first thermally infiltrating a new high-melting-point metal-containing material into the magnet at high temperatures, followed by room-temperature cooling.

In the second step, a low-cost light rare earth (Praseodymium, Pr)-containing material is re-infiltrated into the magnets at high-temperature. A key innovation of this technology is its ability to suppress abnormal grain coarsening, a unique phenomenon that occurred during the grain boundary diffusion process. Such undesirable grain growth degrades the diffusion efficiency and magnetic performance.

The research team successfully controlled this issue, which had been a major limiting factor in conventional GBDP, thereby enhancing diffusion efficiency.

As a result, the diffusion material is rapidly infiltrated into the magnet, significantly improving coercivity. This advancement enables the magnet to achieve performance grades of 45SH to 40UH, equivalent to commercial magnets that contain heavy rare earth elements (HREs), despite using only light rare earth elements.

If this technology is commercialized, it is expected to reduce manufacturing costs while enhancing performance in high-value industries that require high-efficiency motors, such as electric vehicles (EVs), drones, and flying cars.

Dr. Tae-Hoon Kim, the principal investigator of the study, stated, “Currently, the use of expensive heavy rare earth elements in magnets for electric vehicle motors and high-end home appliances is inevitable.

“However, due to the concentration of heavy rare earth resources in specific regions and their high costs, researchers worldwide have been striving for years to develop technologies that can reduce or replace heavy rare earths in magnets—yet progress has remained stagnant.

“By introducing a novel concept, this technology demonstrates the potential to break free from heavy rare earth dependency in high-performance magnet manufacturing. Moreover, it presents a new direction for research on grain boundary diffusion processes, a core technique in the permanent magnet industry.

“If commercialized, this technology will mark the first instance of South Korea securing a dominant position in the most critical aspect of permanent magnet technology.”