- Toyota develops a new magnet for motor that uses less neodymium.
- They have replaced some part of neodymium with less expensive rare earths, cerium (Ce) and lanthanum (La).
- It provides an equivalent level of heat resistance and coercivity, while decreasing the neodymium amount up to 50 percent.
Toyota Motor Corporation revealed the world’s first heat-resistant, neodymium-reduced magnet. It uses less neodymium, and can operate well in extreme temperature scenarios.
Neodymium magnet is rare-earth magnet made of boron, iron and neodymium alloy to form the tetragonal crystalline structure. They are mostly used in several types of motors like high throughput motors commonly used in electric vehicles. And since the trend of electric vehicles is growing rapidly, you can expect high demands of these kinds of motors in the near future.
Neodymium magnets are the one of the strongest permanent magnets which have replaced other magnet types in several modern devices, like magnetic fasteners, hard disk drive and motors in cordless tools.
Neodymium’s production volume is significantly higher among rare earths, there is a high chance of shortage in the future as electric vehicles become increasingly popular. To address this concern, Toyota has developed a technology that tries to decrease the usage of neodymium.
The New Magnet
4th Gen Prius motor | Credit: Toyota
The magnet built by Toyota doesn’t use dysprosium (Dy) or terbium (Tb) that are categorized as critical rare earth materials essential for developing heat-resistant neodymium magnets. They have replaced some part of neodymium with less expensive rare earths, cerium (Ce) and lanthanum (La).
This replacement reduces the amount of neodymium used in the magnet. Neodymium is responsible for high magnetization (known as coercivity) and heat resistance. Decreasing amount of neodymium in greater extent and replacing it with other materials could degrade the performance of the motor.
Keeping this in mind, Toyota built a new technique that suppresses the degradation of heat resistance as well as coercivity, when neodymium is replaced with cerium and lanthanum. They developed a magnet with equivalent heat resistance and coercivity level, while decreasing the neodymium amount up to 50 percent.
The magnet maintains its coercivity even at extreme temperature because of these 3 combinations –
Grain refinement of magnet: The magnet grains’ size is reduced to one-tenth and grain boundary area is increased in order retain the high coercivity level at extreme temperatures.
Image credit: Toyota
2-layered grain surface: The concentration of neodymium is kept higher on the magnet grains’ surface and lower in the core. This reduces the overall amount of neodymium in new magnets, while keeping the level of coercivity almost same.
Cerium and Lanthanum alloy ratio: The company alloyed less expensive and abundant rare earths in a specific ratio – Ce:La = 3:1. This suppresses the deterioration of heat resistance and coercivity.
Along with automobiles and robotics, this new magnet would be used to maintain a balance between the supply and demand of precious rare earth resources.
The company will further enhance the performance and analyze potential applications of the product, while developing the technologies for mass production. For now, their goal is to achieve early adoption in electric motors for several applications.
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Moreover, Toyota will be working to develop the foundation to support the large-scale use of electric vehicles. Elemental technology development for batteries, inverters, motors and other machines will need a lot of research and development, and Toyota plans to make steady growth in every field.
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