Nikkei. Hitachi Metals Ltd. has developed a neodymium magnet that can withstand temperatures more than 20% higher than normal without sacrificing magnetic strength. The new magnet is well suited for high-performance traction motors in hybrid cars, delivering enough magnetic force at high temperatures to design the magnet 20% lighter and reduce the overall weight of the car by several kilograms.
Although neodymium-iron-boron (Nd-Fe-B) materials are desirable for permanent-magnets, the neodymium magnets can lose magnetic energy at fairly modest temperatures and are operating at much less than half of their power by the time they reach 100° C to 125° C.
However, one parameter stipulated by automakers for future electric drive motors is the need to operate well at temperatures up to 200° C. The operation at elevated temperature is to minimize cooling needs, where the increased high-temperature magnetic performance is more critical than room temperature magnetic properties.
Developing a neodymium magnet alloy that withstands high temperature is thus a focus of research interest. In developing a neodymium alloy for magnets, the rare earth element dysprosium can be added to improve heat resistance, but there is a trade-off because this material also reduces the magnetic force of the magnet. (Earlier post.)
The dysprosium is normally added before the magnet is formed into the molten mix of iron, neodymium and boron. But in the new manufacturing process developed by Hitachi Metals, the dysprosium is vapor-deposited in a vacuum onto the magnet after it has been formed. This way the dysprosium seeps between the magnet crystals but is not part of the internal crystal structure.
The process yields neodymium magnets of a given strength that have higher heat resistance than comparable neodymium magnets. It also cuts down on the use of expensive dysprosium.
Hitachi Metals has begun shipping samples and will build equipment for mass production if there is sufficient market interest. The company holds a 50% share of the market for industrial-use neodymium magnets.