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New Toyota magnet cuts rare-earth use

Automaker targets neodymium in new formula for magnets used in electric motors

by Melody M. Bomgardner
February 26, 2018 | APPEARED IN VOLUME 96, ISSUE 9

Credit: Shin-Etsu Chemical
Electric vehicle motors turn with the help of magnets made from rare-earth elements (black).
Credit: Shin-Etsu Chemical
Electric vehicle motors turn with the help of magnets made from rare-earth elements (black).

The rise of electric vehicles is threatening supplies of a host of the earth’s elements. Cobalt and lithium for batteries are getting most of the attention, but rare earths for electric motors are also a pinch point.

Now, Toyota Motor scientists have developed a new recipe for the motors’ permanent magnets that cuts reliance on particularly rare rare earths.

Permanent magnets keep electric motors turning in all kinds of devices, from electric toothbrushes to refrigerator compressors. In electric vehicles, the magnets need to last a long time without demagnetizing. They also have to stay stable at temperatures that can reach 100 ºC.

To meet those requirements, the magnets are made up of 30% rare earths, to take advantage of their many unpaired electrons, and 70% iron. The go-to rare earth for powerful, durable magnets is neodymium.

Most of this pricey element comes from China, and Toyota says demand is expected to increase rapidly. Smaller amounts of terbium or dysprosium are added to neodymium to lend heat resistance, but those elements are even more expensive.

Toyota has already cut terbium and dysprosium use in the 2016 Prius, and future magnets won’t use any, the firm promises. In addition, up to 50% of the neodymium will be replaced with the low-cost rare earths lanthanum and cerium.

To make the new recipe work, Toyota scientists reduced the size of the magnet’s grains to 0.25 micrometers, one-tenth their original size. They then concentrated neodymium on the surfaces of the smaller grains; the grains in standard magnets have the expensive element throughout. Looking inside the grains, they found that a 1:3 ratio of lanthanum to cerium is needed to prevent magnet performance from deteriorating.

Toyota says the new magnets could reach the market in the first half of the 2020s. They could also be used in robots and household appliances.

Rare earth bargains

Lanthanum and cerium are low-cost rare earths.

Cerium $2.34
Lanthanum 2.34
Neodymium 62.66
Dysprosium 176.67

Note: Prices are from October 2017. Sources: Asian Metal, Shanghai Metals Market


Ke Han, a research scientist at the U.S. National High Magnetic Field Laboratory, says Toyota is on the right path to reduce rare earths in permanent magnets. “I think it does take both approaches to do it—replacing some neodymium and reducing the grain size.”

Han would like to go even further. “Most rare earths are not very stable, even at room temperature,” he points out, and removing them completely would result in electric vehicles that last longer. Han is working on combinations of new materials, including manganese and gallium, but says developing non-rare-earth magnets will take years.

Another approach is to skip the permanent magnets entirely. Tesla Motors uses an electric induction motor, which was invented by Nikola Tesla and is aided by electromagnets instead.



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Comments (February 26, 2018 9:03 AM)
This is great news! Dependence on one country for your needs can be problematic and detrimental to overall progress. Than ks to Toyota.
Edmund Metcalfe (February 27, 2018 9:41 AM)
This is extremely poor reporting.
The number two global supplier of Nd-Pr-oxide, the raw material for NdFeB permanent magents is Lynas Corp, who has a world class multi-decade resource in Australia and a environmentally sustainable processing plant in Malaysia. They sell everything they produce.

"Most rare earths are not very stable, even at room temperature"
What the heck does this nonsense even mean? Rare earths are elements. Are we to think they rot? Undergo nuclear transformation at room temp?

There's no eliminating them. 100 kt of NdFeB magnets will be produced this year.
Charles Bruzzone (February 28, 2018 11:36 AM)
The reference is probably to the thermal stability of the magnetic properties of the rare-earth alloy magnets, rather to the stability of the elements themselves. SmCo magnets are typically used for high temperatures applications (above ~150C)to avoid irrecoverable demagnetization, for example. Higher thermal stability magnets provide an advantage in simplification of the thermal design.
Edmund Metcalfe (March 5, 2018 5:41 PM)
This publication is the mouthpiece of the American Chemical Society. It's embarrassing to see such poor reporting.

The SmCo market is 4000 tpa.
Both Sm And Co are more problematic than Nd-Pr.
The NdFeB market is over 100,000 tpa.
Keeping NdFeB is essential, but quite obviously it is not a showstopper for the strongest mass-produced magnets ever. It is extremely unlikely that any stronger magnet will be found that will take its place.
Melody Bomgardner (March 7, 2018 6:53 PM)
Thanks Charles! Yes, the thermal stability of rare earths when inside a motor's permanent magnet is what the story was referring to, the concern is the potential to demagnetize. And the fact that rare earth mines sell everything they make is likely what is concerning to large automakers. It doesn't take much to alter the supply availablibility of certain rare earths at the prices that big users are used to paying. Similarly companies further down the battery supply chain are trying to own their own lithium deposits - and lithium is relatively abundant. Most of the concern is looking out some years into the future.

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