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Replacing neodymium could slash PM motor costs

26 February, 2018

The Japanese car-maker Toyota says that it has developed a magnet that uses much less of the costly rare-earth material neodymium than is normally needed for high-power PM (permanent magnet) motors used in electric vehicles, robots and other applications. It has replaced up to half of the neodymium (Nd), which currently costs around $100 per kilogram, with two other rare-earth materials, lanthanum (La) and cerium (Ce), each costing around $5-7/kg, potentially cutting the cost of PM motors – and their applications – substantially.

The price of neodymium has fluctuated widely in recent years, peaking in 2011 when China ­– which has about 80% of the world’s reserves – imposed export caps on rare-earth materials. There was another spike last year when a clampdown on illegal Chinese mining caused neodymium prices to soar by almost a third in one month.

The price of neodymium is an important factor for Toyota which aims to be selling 5.5 million partly or fully electric vehicles per year by 2030. The company is worried that if demand for neodymium continues to grow, it will become extremely expensive, or supplies will run out. At the current rate of use, demand for neodymium could exceed supplies by 2025.

Announcing the new magnet technology in Japan, Akira Kato, general project manager at Toyota’s advanced r&d and engineering business, warned that “if we continue to use neodymium at this pace, we will eventually experience a supply shortage. We wanted to come up with a technology which would help to conserve neodymium stocks.”

The fourth-generation motors used in Toyota's Prius hybrid-electric cars still have relatively high levels of the costly neodymium rare-earth material

Nd plays a vital role in in maintaining high coercivity (the ability to maintain magnetisation) and heat resistance in magnets. Merely replacing it with La and Ce would affect the magnet’s performance, so Toyota has had to develop new technologies to prevent this from happening when making the substitution. It has also eliminated the use of two other costly rare-earths – terbium and dysprosium.

Toyota is refining the technology to enhance the magnets’ performance further and to develop mass-production technologies. It predicts that the new magnets will have a wide range of applications in motors with relatively high outputs, and expects the first applications to emerge in the early 2020s.

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