R-T-B based permanent magnet

US11657934B2 · kind B2 · utility

Assignee

• TDK CORPORATION · JP

Inventors

• Yuki Nagamine · Tokyo, JP
• Masashi Miwa · Tokyo, JP
• Yoshinori Fujikawa · Tokyo, JP

Key dates

• Filing date: Mar 28, 2019
• Grant date: May 23, 2023
• Expiry date: May 15, 2040

Classification

• Technology area (CPC H): Electricity
• CPC primary: H01F41/0293
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

An R-T-B based permanent magnet, excellent in magnetic properties relatively reducing amount of heavy rare earth element used, wherein R represents rare earth element, T iron group element and B boron, includes main phase grains including R2T14B crystal phase and grain boundaries between main phase grains. Grain boundaries include R—O—C—N concentrated parts where concentrations of R, O, C and N are all higher than in main phase grains. O/R(S)>O/R(C) wherein O/R(S) represents O/R ratio (atomic ratio) in R—O—C—N concentrated parts in a surface of an R-T-B based permanent magnet and O/R(C) represents O/R ratio (atomic ratio) in R—O—C—N concentrated parts in a center of an R-T-B based permanent magnet. A heavy rare earth element RH is in a surface of an R-T-B based permanent magnet as R. R—O—C—N concentrated parts in a surface of an R-T-B based permanent magnet have RH/R ratio (atomic ratio) of 0.2 or less.