Car manufacturer Toyota has unveiled a method to halve the
amount of neodymium used in heat-resistant permanent magnets,
and to entirely avoid the use of the heavy rare-earth
elements terbium and dysprosium.
The technology would give magnet-makers the option of
sourcing their materials from somewhere other than China, and
could ease the soaring demand in the electric vehicle (EV)
sector for traditional magnet rare-earth materials, while
increasing demand for cerium and lanthanum.
The technology would "contribute to reducing the risks of a
disruption in supply and demand of rare earths, and price
increases," Toyota said.
The company expects that the new magnet technology will be
brought into commercial use in the "first half of the 2020s,"
with use in EV motors "within the next 10 years."
|Materials used in the magnet, including
the rare earths.
Rising neodymium demand
Electric-vehicle makers have become increasingly concerned
about the need to use rare-earth permanent magnets in their
motors, because they offer better power-to-weight performance
These magnets are considered essential if EVs are to deliver
the longer driving ranges that vehicle buyers demand, but they
expose manufacturers to rising material costs and the threat of
disruptions to the supply chain.
The most common type of magnet in commercial use is made of
iron and boron, alloyed with the light rare-earth
Neodymium magnets have long been the most affordable, as
well as the strongest, type of rare-earth magnet. But the
prices for neodymium have been increasing rapidly while demand
for such magnets has increased, driven by the EV industry, as
well as for use in generators in wind turbines.
"Production volumes of neodymium are relatively high among
rare earths, but there are concerns that shortages will develop
when electrified vehicles, including hybrid and battery
electric vehicles, become increasingly popular in the future,"
|A fourth generation Prius motor.
In addition, neodymium magnets lose their effectiveness when
exposed to high temperatures, which has the effect of reducing
engine performance in EV applications.
One solution to this loss in performance is the addition of
heavy rare-earth elements such as terbium and dysprosium. But
this solution brings up fresh difficulties of supply.
Heavy rare-earth elements are currently only produced in
China, although Australia’s Northern Minerals
plans to commence pilot production of terbium and dysprosium in
"Terbium and dysprosium are rare and expensive metals, found
in locations with high geopolitical risks," Toyota said.
Toyota has already achieved a significant reduction in the
amounts of terbium and dysprosium used in its electric engine
for the fourth-generation Prius, its hybrid vehicle. But this
reduction was achieved at the cost of even higher neodymium
This new technology, in contrast, not only eliminates the
remaining heavy rare earths, but trades a portion of the
neodymium for lanthanum or cerium.
Neodymium magnets consist of tiny crystallized magnet
grains. The new magnet technology reduces the size of the
magnet grains, in order to preserve coercivity, which is the
ability of the material to hold magnetization.
The new production process also results in grains which have
high concentrations of neodymium on the surface, while the core
of each grain is composed of a cheaper mixture of lanthanum and
"If neodymium is simply alloyed with lanthanum and cerium,
its performance properties [such as heat resistance and
coercivity] decline substantially, complicating the use of
light rare earths," Toyota said.
"As a result of the evaluation of various alloys," it added,
"Toyota has discovered a specific ratio at which lanthanum and
cerium, both abundant and low-cost rare earths, can be alloyed
so that the deterioration of properties is suppressed."
Range of applications
The new technology will perform as well as more traditional
rare-earth magnets, with equivalent heat resistance, Toyota
said, but with as much as half of the neodymium replaced with
lower-priced lanthanum and cerium.
"This new magnet is expected to have a wide range of
applications in motors that require relatively high output,"
Toyota said, "such as those required for EV drive motors and
generators, electric power steering, robots, and various