Cerium Gap Magnets (CGMs). Towards a new castable mass market magnet.

A. Palasyuk, A. Swanson, M. Besser
Ames National Laboratory,
United States

Keywords: cerium, gap magnet, casting, mass market


In commercial permanent magnets, a performance gap exists between costly NdFeB magnets and cheaper ferrite magnets. While ferrite magnets are less costly, they cannot accommodate the size requirements of many magnetic assemblies. Due to these size constraints, NdFeB magnets have gained in popularity and use, resulting in increased consumption of critical elements such as neodymium and dysprosium. However, for the vast variety of applications, these magnets are stronger than they need to be. Efficient processing by simple casting, accompanied with usage of noncritical cerium and reduced amounts of cobalt, allow the new Cerium Gap Magnets (CGMs) to reach price/performance characteristics suitable for the mass market. This creates an opportunity for middle-performing, fully dense and bonded permanent magnets. CGMs eliminate the need to use sintered NdFeB for middle energy applications, i.e., those requiring 10 – 20 Mega Gauss-Oersted (MGOe). It also has the potential to fully substitute bonded NdFeB magnets operating within 4–10 MGOe. In this way critical neodymium is spared for high-energy applications such as wind turbines and electric motors. Size constraints are eliminated because CGMs are more than 400% stronger than ferrite magnets. Cerium Gap Magnets (CGMs) represent an alternative for supply dependent critical rare-earth (RE) magnets. They are domestic, versatile, process effective and less susceptible to supply disruptions. Our experiments show that these magnets easily achieve energy products (BH)max.of 15 – 20 MGOe because of their unique intra-granular coercivity mechanism that does not require typical powder metallurgy. The mechanism is regulated by the 2:7/5:19-type stacking faults and/or intercalated regions that appear in the matrix because of its reduced solubility at low temperatures. This opens potential for simple processing and/or advanced manufacturing. Our casting experiments show that (BH)max. beyond 15 MGOe, with Curie temperatures of >500 oC, remanent magnetizations >8.5 kG and coercivities > 5 kOe, are achievable in one-step procedure that includes vacuum induction melting of kg-scale ingots with precisely controlled cooling process. This technology is among the 100 best technologies of 2023, according to R&D100 Awards.