A Push to Make Motors With Fewer Rare Earths

FOR much of the last century, the straightforward solution to making a car perform better has been to install a bigger engine. In the hybrids and electric cars of coming years, however, the answer might be installing motors with more powerful magnets.

Until the 1980s, the most powerful magnets available were those made from an alloy containing samarium and cobalt. But mining and processing those metals presented challenges: samarium, one of 17 so-called rare earth elements, was costly to refine, and most cobalt came from mines in unstable regions of Africa.

In 1982, when researchers at General Motors developed a magnet based on neodymium, it seemed that an ideal alternative had arrived. While neodymium is also one of the rare earth metals — a misleading name, as they are actually fairly common, just widely dispersed — it is more abundant than samarium, and at the time it was cheaper. When combined with iron and boron, both readily available elements, it produced mighty magnets.

In the electric drive motor of a hybrid car, for instance, just a kilogram, or 2.2 pounds, of neodymium-based magnets can deliver 80 horsepower, enough to move a 3,000-pound vehicle like the Toyota Prius. Neodymium is an ideal magnet material because it helps to retain a magnetic charge during all driving conditions, and when dysprosium is added to the alloy, performance at high temperatures is preserved.

In recent decades, the demand for neodymium has increased sharply, a result of its usefulness in producing the compact, lightweight magnets used in devices like computer hard drives and audio system speakers.

Today, China controls more than 90 percent of the world’s production of rare earth metals and tightly regulates their export. In 2010, China suspended exports of rare earths to Japan over a territorial dispute. The ruckus caused neodymium prices to soar to nearly $500 a kilogram by the summer of 2011, from less than $50 a kilogram at the start of 2010.

Though shipments have resumed and prices have since come down, the supply uncertainties have again prompted a search for alternatives. Companies like Molycorp, which is reopening and expanding its rare-earth mine in Mountain Pass, Calif., about 55 miles south of Las Vegas, are seeking new sources for these metals.

New supplies are not the only searches under way: last week Honda announced that it would start recycling rare earth metals from used car parts like the nickel-metal-hydride batteries used in hybrid cars, which contain small amounts of neodymium along with lanthanum and cerium. In 2011, Toyota said it was developing induction motors that do not require rare-earth magnets.

Nonetheless, said Mark Johnson, an Energy Department scientist, demand for neodymium will continue to outstrip supply, even with recycling programs and new sources, like Malaysian mines, emerging.

In its “Critical Materials Strategy” report, released at the end of 2011, the Energy Department identified five rare earth metals — neodymium and dysprosium among them — as vital for national security and for the nation’s clean energy industries.

NYT