Many magnet consumers want to learn about the industrialization progress of CeFeB magnet and some magnet manufacturers claimed that the CeFeB magnet will become the new generation permanent magnet. However, the pure sintered CeFeB magnet already ended with failure many years ago and the majority of current studies on CeFeB magnet are mainly focused on the (Ce,RE)FeB magnet.
Why CeFeB magnet attracts so much attention in recent years?
Reason No.1: Raw materials cost
PrNd metal accounts for approximately 90 percent of the raw material cost of NdFeB magnets. In year 2010 the rare earth material prices increased more than 5 times, magnet users was facing a huge pressure from the magnet cost and it was an extremely urgent task for them to find a low-cost magnet. The price of Ce is just one-tenth of PrNd, so the research progress of CeFeB magnet regained interests from end-users.
Reason No. 2: Rational utilization of rare earth resources
Cerium is the largest element in global rare earth reserves. The content of Cerium in Bastnasite is generally between 43% and 50%. Cerium has been widely used in polishing powder, hydrogen storage material, fuel cell and alloy steel. Most of rare earth elements are in the form of multiple-element symbiotic. The fast development of NdFeB magnet industry results in serious backlog of Cerium. Therefore the rational utilization of Cerium has risen to a strategic level.
Why pure CeFeB magnet cannot satisfy the requirement?
Numerous studies have demonstrated that the phase composition of CeFeB magnet is very different from NdFeB magnet. The phase in NdFeB magnet includes Nd2Fe14B phase, Nd-rich phase and B-rich phase. Both Nd2Fe14B phase and Nd-rich phase have positive effect on magnetic properties of NdFeB magnet. In addition to the magnetic phase Ce2Fe14B and B-rich phase, there is also a lot of CeFe2 phase in CeFeB magnet, while you can’t find a similar phase in NdFeB magnet. This makes the optimal composition of CeFeB different from the NdFeB system. It should be noted that the CeFe2 phase is detrimental to get high intrinsic coercivity.
For Lanthanides, researchers have prepared the R2Fe14B compound without the radioactive element Promethium and investigated their lattice structure and magnetic properties. The lattice constant of these R2Fe14B phases presents a typical Lanthanide contraction and it will have an impact on Fe-Fe distance. For Ce2Fe14B phase, its lattice constant is significantly lower than the normal trend of Lanthanide contraction and this cause Fe-Fe distance narrowed. Therefore, intrinsic magnetic properties of Ce2Fe14B, such as the Curie temperature and saturation magnetization, will be much lower than Nd2Fe14B due to above factors.
The root cause of abnormal lattice constant and intrinsic magnetic properties in Ce2Fe14B is the mixed valence characteristics of Cerium element. The ground-state electronic configuration of Cerium atom is [Xe]4f15d16s2. The Cerium ion either can exist as Ce3+ ion like regular rare earth ion, or lose one of electron to be Ce4+ ion. Selective site occupancy of Cerium ion in different valance makes the Cerium present a mixed valence state.
The industrialization progress of (Ce, RE) FeB magnet
The pure CeFeB magnet has been proven a failure and the main work is focused on substitute Pr/Nd by Cerium to prepare the (Ce, RE) FeB magnet. The industrialization of (Ce, RE) FeB is mainly conducted by Chinese researchers and high-abundant rare earth permanent magnet. Actually, some of small magnet manufacturers in China were already using Cerium and Lanthanum since many years ago. The Chinese research team proposes dual-main phase technology to develop the (Ce, RE) FeB magnet. The grade of (Ce, RE) FeB magnet includes N45, N40, N38, N35, N33, N30, N28 and N38M. The introduction of Cerium will cause the decrease of intrinsic coercivity and then influences its Curie temperature and application environment. The researchers hope to use combined addition of rare earth elements and addition of other element like Cobalt to enhance the Max. Operating temperature of (Ce, RE) FeB magnet.
