Sintered NdFeB, as the name implies, is an alloy material composed of Nd2Fe14B, a compound composed of three elements: Nd, Fe, and B. .1Fe4B4 phase) and Nd-rich phase (also known as rare-earth-rich phase), of which the Nd2Fe14B phase is the main phase or basic term.
Most rare earth elements (RE) form RE 2Fe14B compounds, which are the basic phase of sintered rare earth iron boron permanent magnet materials, accounting for 96%-98% of sintered rare earth iron boron permanent magnets. All RE 2Fe14B compounds have the same crystal structure, but their magnetic properties are very different. That is to say, adding other rare earth elements to sintered NdFeB to replace neodymium can change some properties of the magnet.
The role of heavy rare earth metal Dy instead of Nd
1. Significantly improve the coercivity of the magnet
The anisotropy field HA of Dy 2Fe14B compound is about 2.14 times higher than that of Nd2Fe14B, so replacing Nd with a small amount of Dy can significantly increase the coercive force Hcj of the magnet. Theoretically, every time 1% (atomic fraction) Dy replaces Nd, the coercive force Hcj of the magnet can be increased by 11.4kA/m, but the increase in coercive force Hcj in practical applications is related to the existence of other components.
2. Reduce the magnetic polarization intensity Js of the magnet, thereby reducing the remanence Br and the maximum magnetic energy product (BH) m
In theory, every time 1% (atomic fraction) Dy replaces Nd, the magnet's magnetic polarization intensity Js decreases by 90mT
3. Reduce the temperature coefficient of magnet remanence Br and maximum magnetic energy product (BH) m
It should be noted that the addition of heavy rare earth element Dy will significantly increase the raw material cost of sintered NdFeB permanent magnets, so the relationship between cost and magnet performance needs to be comprehensively considered.