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Brief Introduction to Ce-Containing Sintered Nd-Fe-B Magnets

Moye Zhu   2024/01/26

Cerium (Ce), a high-abundance Rare Earth (RE) element, attracts significant attention in research and development efforts aimed at expanding the world of magnetic materials. This is primarily due to Neodymium (Nd), a relatively limited element, has become increasingly relied upon driven by the growing demand for Neodymium Iron Boron (NdFeB) magnets, the most favored super-strong permanent magnets used extensively in consumer electronics, electric motors, generators, wind turbines, and hard disk drives. This overreliance on Nd and underutilization of Ce has led to an imbalanced consumption of symbiotic RE resources in minerals. It is not ideal for sustainable resource management.

Additionally, the overstocked Ce has put downward pressure on its prices while the overused Nd has driven up its prices, making Ce much cheaper than Nd to ensure market balance. 

To make the best of RE and reduce costs, Ce-containing sintered Nd-Fe-B magnets are always ready to make their mark in the magnetic industry.

However, some challenges need to be addressed before Ce-containing sintered Nd-Fe-B magnets contribute significantly to the industry.

The inclusion of Ce in magnets leads to a deterioration in magnetic performance and a degradation in temperature resistance. As shown in Figure 1, the intrinsic properties of RE2Fe14B with different RE compounds demonstrate that the saturation magnetization, magnetic anisotropy field, and Curie temperature of Ce2Fe14B are lower than those of Nd2Fe14B. Moreover, Ce is more reactive and prone to oxidation than Nd and the microstructure of Ce-containing sintered Nd-Fe-B magnets is further away from the desired state compared to sintered Nd-Fe-B.

The intrinsic properties of RE2Fe14B compounds at 22

(Figure 1, the intrinsic properties of RE2Fe14B with different rare earth element compounds.)

These factors indicate that the upgrading of production equipment and advanced techniques, as well as a deep understanding of the mechanisms in Ce-containing magnets, are technically required for Ce-containing magnets to achieve the properties comparable with those of sintered Nd-Fe-B magnets.

Otherwise, Ce-containing sintered Nd-Fe-B magnets may only be graded as N35 to N42, and even lower grades like N25 to N30 with coercivities below 10kOe, although they have helped bridge the performance gap between high-performance magnets and ferrites, having created more options for applications that require magnetically adhesive properties, such as magnetic toys, door latches, luggage clasps, and magnetic separators.

Currently, as the development is going gradually, the potential for Ce-containing magnets has been realized as shown in Figure 2. With multiple grades of high magnetic properties, they have a wide range of applications like motors for robotics, machinery, healthcare, energy-efficient appliances, electric bicycles, etc. Grades like N45H and N48M have entered the market and are now playing a vital role in applications such as audio electronics, mobile devices, wind power, and nuclear magnetic resonance. In late May 2022, a 1.5MW wind turbine in Ningxia, China, became operational using 1 ton of Ce-containing magnets.

(Figure 2, Grades of Ce-Containing Sintered Nd-Fe-B Magnets

Using Grain Boundary Diffusion (GBD) technology, Ce-containing magnets can achieve the grades of SH, UH even EH with high-temperature resistance and high coercivity. This enables them to be used in mining machinery, industrial motors, hoists, air conditioning compressors, and more.

In summary, the abundant and cost-effective Ce elements in RE, combined with technological advancements, make Ce-containing magnets play a crucial role in the development of permanent magnets. Increasing the demand for Ce-containing Sintered Nd-Fe-B magnets will release the pressure on the need for Sintered Nd-Fe-B magnets, leading to a more balanced and prosperous permanent magnet industry.

For more information about Ce-Containing Sintered Nd-Fe-B magnet, please feel free to contact us.

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