A permanent magnet alloy being developed by scientists at the U.S. Department of Energy's Laboratory in Ames, Iowa, promises high- temperature performance for next-generation drive motors for electric vehicles. The alloy retains much of its magnetic strength at 200°C to help make electric drive motors more efficient and cost-effective.

According to Ames senior metallurgist and Iowa State University adjunct professor Iver Anderson, current-generation magnets lose much of their magnetic energy at fairly modest temperatures and operate at half of their power once they reach 100 to 125°C. He explained that the most desirable permanent-magnet materials are neodymium-iron-boron magnet materials based on a 2-14-1 crystal structure. "Our challenge was to design a high-performance 2-14-1 permanent magnet alloy that would operate with good magnetic strength at 200°C," said Anderson.

The alloy developed by the Ames scientists uses a mixed rare earth composition. "We used a combination of neodymium, yttrium and dysprosium because they all form 2-14-1 crystal structures," said Anderson. "Together they have much less degradation of their magnetic properties with temperature due to the influence of the yttrium and dysprosium. The alloy lends itself to injection molding, making it economically feasible for mass-producing electric drive motors.

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