NdFeB permanent magnets, known as the "king of magnets" for their ultra-high magnetic energy product and high coercivity, are core functional materials widely used in new energy vehicles, wind power generation, electronic equipment and other fields. Neodymium oxide (Nd₂O₃), as a key raw material and additive for NdFeB preparation, plays an irreplaceable role in raw material supply, microstructure regulation and macro-performance optimization. Its action mechanism and addition ratio directly determine the magnetic properties, stability and service life of the magnets.

I. Core Action Mechanism of Neodymium Oxide

Firstly, it provides the core rare earth neodymium element to build the foundation of main phase magnetic properties. The core magnetic phase of NdFeB permanent magnets is the tetragonal Nd₂Fe₁₄B, and neodymium (Nd) is an essential rare earth element for this main phase. Although neodymium oxide itself is non-magnetic, it can be reduced to metallic neodymium during the preparation processes such as NdFeB smelting and reduction diffusion, combining with iron and boron atoms to form the Nd₂Fe₁₄B lattice. The 4f electron layer of Nd³⁺ has a unique electronic configuration, which forms a strong d-f electron exchange coupling effect with the 3d electrons of Fe atoms, providing high local magnetic moment for the magnet and endowing it with strong uniaxial magnetic anisotropy.

Secondly, it regulates the grain boundary structure and enhances magnetic domain pinning and coercivity. In industrial production, neodymium oxide is also often used as an additive directly in the form of oxide to participate in the regulation of the magnet's grain boundary microstructure. During sintering, part of neodymium oxide reacts with iron and neodymium in the matrix to form neodymium-rich oxide phases, which are distributed at the grain boundaries of Nd₂Fe₁₄B main phase grains in the form of thin films and particles, refining grains and pinning magnetic domain walls.

II. Recommended Addition Ratio of Neodymium Oxide

The addition ratio needs to be precisely controlled according to the magnet performance grade and application scenario. When used as the main phase neodymium source, the proportion of metallic neodymium reduced from neodymium oxide is 28%-32% for high-performance NdFeB (N35-N52 series), 25%-28% for general-purpose NdFeB, and 30%-33% for hot-deformed and nanocrystalline NdFeB. When used as a grain boundary additive directly in oxide form, the recommended ratio is 0.5%-1% for conventional sintered NdFeB, 1%-2% for high-temperature resistant and high-coercivity magnets, and less than 0.5% for rapidly quenched bonded NdFeB.

III. Conclusion