Tailored synthesis in nanoparticle permanent magnets (NPPMs)

(Top) Powder X-ray diffraction patterns and (bottom) hysteresis loops of as-washed and consolidated material.

CMI researchers from the Ames National Laboratory conducted the activity for this highlight

Innovation
Direct conversion of Sm₂O₃ into Sm₂Fe₁₇ phase via reduction-diffusion (RD) produces pure Sm₂Fe₁₇N₃ powders with improved hard-magnetic properties.

Achievement
Developed dispersant-assisted reduction diffusion (RD) approach to improve hard magnetic properties and phase purity. RD at 950°C produced high-purity (98%) Sm₂Fe₁₇N₃ powders that on sintering produced a bulk magnet with (BH)max = 16.5 MGOe and 86% relative density.

Significance and Impact

Criticality and cost: the material is mostly Fe (~74% wt.%) and non-critical rare earth, Sm, as well as earth-abundant nitrogen.
When fully developed, single grain-single particle Sm₂Fe₁₇N₃-based materials are expected to partially replace heavy rare earth Nd-based magnets in high performance, high temperature applications due to superior temperature dependence and likely lower cost.

Hub Goal Addressed
Reducing critical rare-earth content in permanent magnets through development and deployment of novel magnets with improved hard-magnetic properties.

R. Kuchi, D. Schlagel, T. S. Cozzini, J. V. Zaikina, I. Z. Hlova, “Exploiting Mechanochemical Activation and Molten-Salt-Assisted Reduction-Diffusion Approach in Bottom-up Synthesis of Sm₂Fe₁₇N₃," J. All. Comp., 2023, in press. https://doi.org/10.1016/j.jallcom.2024.173532