Dysprosium-Free High-Performance Samarium-Cobalt Magnets for Motors

Traction motors for hybrid and electric vehicles, rolling stock, and industrial equipment operate at relatively high temperatures. Heat-resistant neodymium magnets are therefore generally used for these applications.

However, dysprosium, a key material of neodymium magnets, has high supply risk. In order to rectify this situation, Toshiba has developed samarium-cobalt (SmCo) magnets with higher magnetic force by using a unique heattreatment technology. The newly developed SmCo magnets exhibit a maximum energy product of 280 kJ/m³ at room temperature, the highest level in the world for SmCo magnets under laboratory conditions^(*).

This strong magnetic force has been achieved by increasing the weight content of iron (Fe) in the magnet from 10–15% to 20–25% and by homogenizing and refining the crystal grains through an original heat-treatment process. We have also controlled the powder particle size of the raw material in order to reduce the content of oxides in the magnets.

These magnets, which are now commercially available, are well suited for rolling stock applications.

Transmission electron microscope (TEM) images of conventional
and newly developed high-iron-concentration SmCo magnets

Demagnetization curves of SmFeCo magnets

(*) As of February 2014 (as researched by Toshiba)