Researchers Triple Coercivity Gain in Ce-Rich NdFeB Magnets With Grain-Boundary Engineering

Highlights

• Conventional DyHx diffusion in 13 wt.% Ce magnets yielded only 217.7 kA/m coercivity gain due to CeFe₂ trapping dysprosium at grain boundaries
• A two-step process using Pr-Al-Ga alloy pretreatment followed by DyHx diffusion achieved a combined 706.3 kA/m coercivity increase—more than triple the baseline
• The approach was also validated with TbHx, suggesting broad applicability beyond dysprosium
• Strategic implication: more cerium substitution plus more efficient Dy/Tb use could simultaneously reduce pressure on multiple critical rare earth inputs
• Commercial viability still requires evidence on manufacturing yield, cost, temperature performance, and mass-production scalability

Researchers led by Qing Feng and Zhongwu Liu (opens in a new tab), both at South China University, and colleagues report a potentially important advance in making high-performance Nd-Ce-Fe-B permanent magnets with more cerium and more efficient use of scarce heavy rare earths. Published in Materials Horizons, the study examined magnets containing 13 wt.% Ce, where conventional dysprosium grain-boundary diffusion has struggled to deliver large coercivity improvements.

Zhongwu Liu, Department of Metallic Materials Science and Engineering, School of Materials

The researchers identified the culprit: an intergranular CeFe₂ phase effectively traps dysprosium, leaving less Dy available to form the Dy-rich shells around magnetic grains that protect magnets against demagnetization. Conventional DyHₓ diffusion increased coercivity by only 217.7 kA/m.

Their solution was a two-step process. First, a Pr-Al-Ga alloy was used to reshape the grain boundaries and substantially reduce CeFe₂. That alone increased coercivity by 205.6 kA/m.

Subsequent DyHₓ diffusion added another 500.7 kA/m, producing a combined 706.3 kA/m coercivity increase—more than three times the improvement from DyHₓ diffusion alone. The researchers also demonstrated the approach using TbHₓ, suggesting it may extend beyond dysprosium.

South China University

REEx Insight — Making Cheap Cerium Work Harder

The strategic importance is substitution plus thrift. Cerium is far more abundant than NdPr, while Dy and Tb are expensive, supply-constrained heavy rare earths. If manufacturers can incorporate more Ce while using Dy/Tb more efficiently, they could potentially reduce pressure on several critical magnet inputs simultaneously.

But this remains a materials-science result, not a commercial breakthrough. Investors still need evidence on manufacturing yield, cost, heavy-rare-earth consumption per magnet, temperature performance, and mass-production scalability.

REEx Bottom Line: The study attacks an increasingly important question: not merely how to obtain more rare earths, but how to extract more magnetic performance from the rare earths already available.