Sm2Fe17N3 as a cost-effective high performance magnet

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CMI researchers at Ames Laboratory conducted the research for this highlight

Achievements

  • Demonstrated a 40 °C enhancement of the thermal stability of (Sm1-xRx)2Fe17N3, where R = La and Ce, and x = 0.25. When R = La, magnetic properties comparable to the parent Sm2Fe17N3 are retained, as evidenced by Hc = 16-19 kOe and BHmax = 8.5-8.7 MGOe.
  • Discovered that high-pressure nitrogenation achieves stoichiometry of 3 nitrogen atoms per formula unit, required for best permanent magnet performance, and suppresses precipitation of soft a-Fe.
  • Developed synthesis protocols that consistently yield Sm2Fe17N3 with >95 % purity in 1 g quantities with Hc of 20-25 kOe and BHmax approaching 10 MGOe.

Significance and impact

  • Criticality and cost: mostly Fe (~74% wt.%), and abundant, non-critical  rare earths – Sm, La, and Ce.
  • Strong competitor of Nd-based magnets with comparable, and potentially better permanent magnet properties.

Details and next steps
Enhance thermal stability by co-doping with transition metals and p-block elements, such as Si and Al.

Effect of 25% La/Ce substitution for Sm on thermal stability – increase of decomposition temperature by 40 K.
Effect of 25% La/Ce substitution for Sm on thermal stability – increase of decomposition temperature by 40 K.