Heavy rare earth elements (HREEs) play a crucial role in enhancing the performance of high-performance NdFeB magnets, providing essential support for their use in new-energy vehicles, wind power generation, and other advanced applications.
Definition of Heavy Rare Earth Elements
Heavy rare earth elements refer to a subset of the rare‑earth elements with atomic numbers 64–71, namely gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y). Because they are relatively scarce in the crust, possess distinctive chemical properties, and have high industrial value, they are classified separately. Heavy rare earth elements are widely employed in the field of high‑performance NdFeB magnets.
Effects of Heavy Rare Earth Elements on the NdFeB Magnets
The addition of heavy rare earths—especially dysprosium (Dy) and terbium (Tb)—affects NdFeB magnets in several important ways:
Increased Coercivity
Dy and Tb exhibit magnetocrystalline anisotropy fields far higher than those of the NdFeB main phase. When introduced, they form a heavy‑rare‑earth‑rich shell at grain boundaries, effectively suppressing the nucleation and propagation of reverse‑magnetization domains. This markedly raises coercivity, particularly improving resistance to demagnetization at elevated temperatures. For instance, incorporating heavy rare earths can boost coercivity by more than 20%.
Improved Temperature Stability
Heavy rare earths raise the Curie temperature of the magnet and slow the degradation of magnetic properties with rising temperature. Consequently, magnets containing heavy rare earths retain high coercivity even at high temperatures, making them suitable for high-temperature applications, such as electric-vehicle powertrains.
Fine‑Tuning of Remanence and Energy Product
Excessive addition of heavy rare earths may reduce remanence (Br) and the maximum energy product ((BH)max). However, by precisely controlling the processing—e.g., using grain‑boundary diffusion techniques—the increase in coercivity can be achieved while minimizing the loss of Br and (BH)max.
Influence of Heavy Rare Earth Elements on Production Technologies for NdFeB Magnets
The presence of heavy rare earth elements has driven significant advances in grain‑boundary diffusion (GBD) technology.
Stimulating Process Optimization and Innovation
Because Dy, Tb, and other heavy rare earth elements are expensive, manufacturers and research institutions continuously seek ways to reduce their usage. GBD’s core advantage lies in precisely delivering heavy rare earth elements to grain boundaries, thereby lowering the overall consumption while still enhancing magnetic performance. Optimized diffusion processes can substantially reduce heavy-rare-earth consumption, thereby reducing material costs without sacrificing performance.
Development of Alternative Diffusion Agents
The cost pressure has spurred research into low‑cost diffusion agents. Industrial practice currently employs heavy‑rare‑earth fluorides, hydrides, or pure metals as diffusion sources; these are effective but costly.
Recently, alloys based on light rare earths (e.g., praseodymium‑neodymium) and non‑rare‑earth compounds have been explored as cheaper diffusion agents. While these alternatives lower material expense, challenges remain in achieving comparable diffusion efficiency and long‑term stability. Continued progress is expected to broaden their industrial adoption and lessen dependence on heavy rare earths.
Process and Equipment Upgrades
To improve heavy‑rare‑earth utilization, companies refine GBD processes and upgrade equipment. Such process and equipment improvements boost production efficiency, lower unit costs, and accelerate the commercialization of GBD technology.
Impact of Heavy Rare Earth Elements Prices on the Cost of NdFeB Magnets
Fluctuations in the prices of heavy rare earths (Dy, Tb) have a pronounced effect on the market price of high‑performance NdFeB magnets.
High Share of Raw‑Material Costs
Heavy rare earth elements are essential additives for raising coercivity and high‑temperature stability. In the overall cost structure of high‑performance NdFeB magnets, rare‑earth raw materials (including Pr‑Nd, Dy, Tb, etc.) account for more than 90 % of the total. Although the proportion of heavy rare earths within that share is relatively small, their price volatility significantly influences the total material cost, directly driving up the price of NdFeB magnets.
Policy and Market Supply‑Demand Dynamics
China imposes export controls on Dy, Tb, and other heavy rare earth elements, while supply disruptions in Myanmar’s mines have tightened global availability, causing sharp price increases. Simultaneously, burgeoning demand from emerging sectors such as new‑energy vehicles has intensified the supply‑demand imbalance, further pushing heavy‑rare‑earth prices upward and raising the cost of high‑performance NdFeB magnets.
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