Toyota’s new magnet claims to reduce use of rare-earth element by up to 50%
Toyota claims to have developed the world's first neodymium-reduced, heat-resistant magnet. Neodymium magnets are used in various types of motors, including the high-output motors found in electric vehicles (EVs), use of which is expected to expand. The new magnet reportedly uses significantly less neodymium, a rare-earth element, and can be used in high-temperature conditions.
The company says that new magnet uses no terbium (Tb) or dysprosium (Dy)—both are rare earths that are also categorized as critical materials necessary for highly heat-resistant neodymium magnets. According to the company, a portion of the neodymium was replaced with lanthanum (La) and cerium (Ce), which are low-cost rare earths, reducing the amount of neodymium used in the magnet.
Neodymium plays an important role in maintaining high coercivity (the ability to maintain magnetization) and heat resistance. Merely reducing the amount of neodymium and replacing it with lanthanum and cerium results in a decline in motor performance. Accordingly, Toyota says it has adopted new technologies that suppress the deterioration of coercivity and heat resistance, even when neodymium is replaced with lanthanum and cerium, and developed a magnet that has equivalent levels of heat resistance to earlier neodymium magnets while reducing the amount of neodymium used by up to 50%.
The new magnet can reportedly maintain coercivity even at high temperatures because of the combination of the following three new technologies:
- Grain refinement of magnet: It is now possible to retain high coercivity at high temperatures by reducing the size of the magnet grains to one-tenth or less of those found in conventional neodymium magnets and by enlarging the grain boundary area.
- Two-layered high-performance grain surface: In a conventional neodymium magnet, neodymium is spread evenly within the grains of the magnet, and in many cases, the neodymium used is more than the necessary amount to maintain coercivity. Thus, it is possible to efficiently use neodymium by increasing the neodymium concentration on the surface of the magnet grains, which is necessary to increase coercivity, and decreasing the concentration in the grain core. This results in the reduction of the overall amount of neodymium used in the new magnet.
- Specific alloying ratio of lanthanum and cerium: If neodymium is simply alloyed with lanthanum and cerium, its performance properties (heat resistance and coercivity) decline substantially, complicating the use of light rare earths. As a result of the evaluation of various alloys, Toyota 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.
This Nd-reduced, heat-resistant magnet, which incorporates all three of the technologies described here, is expected to aid in expanding the use of motors in areas such as automobiles and robotics, as well as maintaining a balance between the supply and demand of valuable rare earth resources. Toyota says it will work to further enhance performance and evaluate application in products while accelerating the development of mass production technologies.
The company expects that the magnets will be put to use in the motors of electric power steering for automobiles and other applications in the first half of the 2020s. Additionally, the company plans to undertake development with the aim of practical application in high-performance electrified vehicle drive motors within the next 10 years.