In recent years, sintered Nd - Fe - B technology has been constantly evolving, and the comprehensive performance of magnets has been steadily improving. With the increasingly wide application of sintered Nd - Fe - Bin high - performance motors, magnets with high energy product and high operating temperature have become the core objectives of research and development. On the other hand, in order to improve the balanced utilization level of rare - earth resources and reduce the cost of magnets, high - abundance magnets have also become another important research and development objective with Chinese characteristics.
The new technologies mainly include methods such as Grain Boundary Diffusion (GBD), Grain Boundary Modification (GBM) and dual (multiple) alloys (including dual - main - phase) aimed at optimizing the grain boundary, as well as the grain refinement method aimed at high coercivity of near - single - domain particles. In addition, the wide - spread adoption of oxygen - content - control technology has also laid the foundation for the preparation of high - performance sintered Nd - Fe - B magnets.
After the adoption of the above - mentioned new processes, double - high sintered Nd - Fe - B magnets have been successfully developed and produced. In April 2013, Zhongke Sanhuan published an article announcing that it had successfully developed a double - high sintered Nd - Fe - B magnet using the GBD process, with its room - temperature magnetic performance reaching an intrinsic coercivity Hcj = 35.2 kOe and a maximum energy product (BH)max = 40.4 MGOe. In June 2018, Shin - Etsu Chemical announced that it had used the grain - refinement technology to grind Nd - Fe - B alloy powder to 2.6 ｍｍ and successfully prepared a sintered Nd - Fe - B magnet without heavy rare - earth elements with Hcj = 17 kOe; and the Hcj was increased to 26 kOe by using the grain - boundary - diffusion process. In terms of low cost, Central Iron and Steel Research Institute and Zhongke Sanhuan have respectively successfully obtained sintered Nd - Fe - B magnets with added Ce or mixed rare - earth elements with high cost - performance using the dual - main - phase method; Ningbo Institute of Materials has successfully prepared a sintered Nd - Fe - B magnet with added Y.
