Sm2Co17

Sm2Co17 is a permanent magnet compound consisting of samarium and cobalt with the formula Sm2Co17. It is part of the samarium–cobalt (Sm–Co) magnet family and was developed for high-temperature, high-coercivity applications. The material crystallizes in the Th2Zn17-type hexagonal structure. In practice, commercial magnets are often slightly off-stoichiometric and include small additions of copper, iron, and zirconium (for example Sm2(Co,Fe,Cu,Zr)17) to optimize grain boundary diffusion and coercivity.

Properties: The Sm2Co17 phase provides strong magnetic anisotropy and a high energy product, typically in the mid-to-high tens of MGOe depending on processing. The magnets exhibit excellent resistance to demagnetization and maintain magnetic performance at elevated temperatures compared with many neodymium magnets. They are, however, relatively brittle and require protective coatings to resist oxidation. They also show good corrosion resistance for a cobalt-based magnet.

Manufacture: Production uses powder metallurgy. Sm- and Co-based alloy is melted and atomized into powders, which are compacted and sintered. Post-sintering diffusion treatments—often with Cu, Fe, and Zr—develop a magnetocrystalline microstructure that enhances coercivity. The magnets are then machined and magnetized.

Applications and history: Developed in the 1960s by companies in Japan and the United States, Sm2Co17 magnets provided high-temperature performance before the rise of neodymium-iron-boron magnets. They are widely used in aerospace, defense, and automotive applications requiring stable magnetism at elevated temperatures.

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