Low-Rare-Earth NdFeB Magnets Gain 25% Energy Product With Cool-and-Reheat Sintering

Highlights

• Interrupted two-step sintering with intermediate cooling raised NdFeB energy product from 41.48 to 51.70 MGOe—a 25% gain.
• Total rare-earth content held at just 28.6%, demonstrating rare-earth thrifting without sacrificing magnetic output.
• Study is a preprint from NIMTE-CAS; factory-scale yields, energy economics, and long-term performance remain unproven.
• Rare-earth thrifting could reduce NdPr demand per magnet but may expand the addressable market for NdFeB motors, leaving aggregate demand uncertain.

Hui Cao of Ningbo University and researchers led by Shuai Cao and Shuai Guo at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences (opens in a new tab) (NIMTE-CAS), report (opens in a new tab) a simple-looking way to get more performance from NdFeB magnets while using a low 28.6% total rare-earth content. Instead of keeping the magnet hot through two sintering stages, the researchers cooled it completely between them. That extra cooling step helped remove tiny pores, align magnetic grains, and limit unwanted grain growth. Compared with continuous two-step heating, maximum energy product jumped from 41.48 to 51.70 MGOe, while remanence increased from 14.73 to 15.11 kGs. The result is promising for reducing rare-earth intensity, but this is a non-peer-reviewed preprint, not yet a factory-scale breakthrough.

REEx Insight: The Cheapest Rare Earth May Be the One You Don't Need

Could the commercial lesson be easy to miss? Western supply-chain policy largely asks: How do we mine and separate more NdPr? China is simultaneously working on another question: How do we manufacture the same magnetic output with less rare-earth material? Recent Chinese research identifies reduced rare-earth consumption and microstructure control as major permanent-magnet research priorities.

This study matters because it attacks material productivity, not just supply. Lowering rare-earth content increases the share of the magnetically powerful Nd₂Fe₁₄B phase. But push too far and there is too little Nd-rich material between grains: pores remain, grains grow badly, and coercivity falls.

Cooling may offer a manufacturing workaround. The Nd-rich material solidifies, then melts again during reheating and redistributes around pores and grain boundaries. In simple terms, the researchers appear to make a small amount of rare-earth-rich material work harder.

For investors, that has two opposing implications. Successful rare-earth "thrifting" could reduce NdPr required per unit of magnet output—moderating future demand intensity. But it could also make NdFeB motors cheaper and expand their addressable market. Less NdPr per magnet does not automatically mean less aggregate NdPr demand.

Cool, Reheat, Improve

The winning process heated magnets at 1,070°C for five hours, cooled them to room temperature, then reheated them at 1,085°C for three hours. Density rose from 7.48 to 7.56 g/cm³, while better grain alignment helped lift magnetic performance.

There is a tradeoff. Coercivity was 7.89 kOe, versus 8.06 kOe after presintering alone. The study also did not demonstrate factory-scale yields, energy economics, cycle time, corrosion resistance, or long-term motor performance. An extra complete cooling-and-reheating cycle could increase manufacturing time and energy consumption.

REEx Connect

The authors report no known competing financial interests. Funding came from China's Advanced Materials–National Science and Technology Major Project, Ningbo's Beilun District, Jiangxi Province, and the National Natural Science Foundation of China.

Citation: Cao H. et al. Enhanced Densification and Remanence in Reduced-Rare-Earth-Content Sintered Nd-Fe-B Magnets Enabled by Interrupted Two-Step Sintering with Intermediate Cooling. SSRN preprint, 2026.