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Electric vehicle motor cuts use of rare earth by 40%

20 November, 2012

The Japanese car-maker Nissan has developed an electric motor that cuts the use of the rare-earth element dysprosium (Dy) by 40% compared to conventional EV (electric vehicle) motors. The environmentally-friendly motor will power an updated version of Nissan’s Leaf EV, just released in Japan.

EV motors need to be compact and to deliver high performance, and to achieve this they usually incorporate powerful neodymium-based (NdFeB) magnets. Dysprosium is added to these magnets to strengthen their heat resistance. In the new motor – developed jointly by Nissan and its suppliers – instead of adding the dysprosium to the magnets evenly, a new process distributes it around each crystal grain`s boundary, improving the magnet`s heat resistance while maintaining good performance. In the diagram (below) the volume of Dy distribution on the crystal grains is shown in orange.

The result is a 40% reduction in dysprosium use while still keeping heat-resistance levels comparable to those of conventional motors.

Dysprosium resources are limited. As the demand for EVs and domestic appliances using permanent magnet motors grows, so will the demand for dysprosium. Nissan says that its new motor is the first step in a process of limiting its use of rare-earth elements. The company plans to adopt the grain boundary diffusion process for its hybrid vehicle motors, with the ultimate goal of eliminating the use of dysprosium in other components as well.

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