R-T-B based permanent magnet

US11152142B2 · 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: Oct 19, 2021
• Expiry date: Nov 25, 2039

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C22C2202/02
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

An R-T-B based permanent magnet excellent in magnetic properties relatively reduces the amount of a heavy rare earth element used. An R-T-B based permanent magnet, wherein R represents a rare earth element, T an iron group element and B boron, includes main phase grains including an R2T14B crystal phase and grain boundaries formed 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 those in main phase grains. C/R(S)>C/R(C) is satisfied in which C/R(S) represents a C/R ratio (atomic ratio) in R—O—C—N concentrated parts present in a surface of a R-T-B based permanent magnet and C/R(C) represents a C/R ratio (atomic ratio) in the R—O—C—N concentrated parts present in the center of a R-T-B based permanent magnet, and a heavy rare earth element RH is included in the R-T-B based permanent magnet.