R-t-b sintered magnet

By controlling the thickness distribution of the two grain boundaries and optimizing the composition of RTB-based sintered magnets, the problems of HcJ reduction and unstable supply of heavy rare earth elements at high temperatures were solved, achieving magnet performance with high HcJ and high Br, and reducing dependence on heavy rare earth elements.

CN120917530APending Publication Date: 2025-11-07PROTERIAL LTD
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Patent Information

Application Number
CN202480023334.2
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Priority Date
2023-03-30
Filing Date
2024-03-14
Publication Date
2025-11-07

AI Technical Summary

Technical Problem

RTB-based sintered magnets suffer from reduced coercivity (HcJ) at high temperatures and unstable supply of heavy rare earth elements. Existing technologies struggle to increase HcJ and maintain high remanent flux density (Br) without using heavy rare earth elements.

Method used

By controlling the thickness distribution of the two grain boundaries, the specific methods include measuring the frequency histogram of the grain boundary width on the cross section of the RTB-based sintered magnet, limiting the frequency of the grain boundary width below 0.03 μm to below 12% of the total, controlling the content of heavy rare earth elements Dy and Tb to below 0.5% by mass, optimizing the composition ratio of T and B, and ensuring the uniformity of the grain boundary phase.

Benefits of technology

It achieves the maintenance of high coercivity HcJ and high remanent magnetic flux density Br at high temperatures, while reducing the dependence on heavy rare earth elements and improving the quality and stability of the magnet.

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Abstract

This R-T-B sintered magnet has: a main phase comprising a plurality of R2T14B compound particles; and a grain boundary phase located between the plurality of R2T14B compound particles and including a two-particle grain boundary and a grain boundary trident point. In a frequency histogram of grain boundary widths measured from N reference points included in grain boundaries of two particles located in a cross-section including the orientation direction of the R-T-B sintered magnet in a plane, the group distance is determined such that the sixth group represents a mode from the lowest group. The total frequency of the first packet, the second packet, and the third packet from the lowest packet is 12% or less of the total frequency.
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Citation Information

Patent Citations

  • Method for analyzing polycrystalline material

    JP2019015573A

  • Alloy for r-t-b-based rare earth sintered magnet, process for producing alloy for r-t-b-based rare earth sintered magnet, alloy material for r-t-b-based rare earth sintered magnet, r-t-b-based rare earth sintered magnet, process for producing r-t-b-based rare earth sintered magnet, and motor

    WO2013008756A1