R-T-B based permanent magnet
An R-T-B permanent magnet that contains: main-phase grains composed of an R 2 T 14 B compound (where R is a rare earth element, T is a transition metal element, and B is boron); and grain boundaries. R includes Ce. The grain boundaries include multi-grain grain boundaries that are adjacent to three or more main-phase grains. The multi-grain grain boundaries include an R-rich phase, and lamellar or acicular R-T precipitates are present in the R-rich phase.
1 . An R-T-B based permanent magnet comprising main phase grains including an R 2 T 14 B (compound, in which R includes a rare earth element, T includes a transition metal element, and B represents) boron, and a grain boundary, wherein
R at least includes Ce,
the grain boundary includes a grain boundary multiple junction surrounded by three or more main phase grains, and
the grain boundary multiple junction includes an R-rich phase, the R-rich phase includes an R-T deposit of a plate shape or a needle shape, and 30.0% or more of the circumference of the R-T deposit is covered in the R-rich phase in one cross-section of the R-T-B based permanent magnet.
2 . The R-T-B based permanent magnet according to claim 1 , wherein the R-T deposit includes Ce.
3 . The R-T-B based permanent magnet according to claim 1 , wherein a number density of the grain boundary multiple junction including the R-rich phase including the R-T deposit in one cross section of the R-T-B based permanent magnet is 1000 per mm 2 or more.
4 . The R-T-B based permanent magnetic according to claim 1 , wherein an amount of Ce to R in the R-T-B based permanent magnet is within a range of 15 mass % or more and 25 mass % or less.
5 . The R-T-B based permanent magnet according to claim 1 , wherein the R-T-B based permanent magnet include substantially neither La nor Y.
6 . The R-T-B based permanent magnetic according to claim 1 , wherein the R-T-B based permanent magnet includes at least one selected from Al and Ga.
7 . The R-T-B based permanent magnetic according to claim 6 , wherein the R-T-B based permanent magnet includes carbon.
8 . The R-T-B based permanent magnetic according to claim 1 , wherein a total amount of R is within a range of 30.00 mass % or more and 34.00 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.
9 . The R-T-B based permanent magnetic according to claim 1 , wherein an amount of B is within a range of 0.70 mass % or more and 0.95 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.
10 . The R-T-B based permanent magnetic according to claim 1 , wherein an amount of Co is within a range of 0.50 mass % or more and 3.00 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.
11 . The R-T-B based permanent magnetic according to claim 1 , wherein an amount of Ga is within a range of 0 mass % or more and 0.60 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.
12 . The R-T-B based permanent magnetic according to claim 1 , wherein an amount of Al is within a range of 0.20 mass % or more and 1.00 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.
13 . The R-T-B based permanent magnetic according to claim 1 , wherein an amount of Cu is within a range of 0 mass % or more and 0.50 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.
14 . The R-T-B based permanent magnetic according to claim 1 , wherein an amount of Zr is within a range of 0.10 mass % or more and 1.00 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.
15 . The R-T-B based permanent magnetic according to claim 1 , wherein a total amount of heavy rare earth elements included as R is within a range of 0 mass % or more and 0.10 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.
16 . The R-T-B based permanent magnetic according to claim 1 , wherein an amount of C may be within a range of 0 mass % or more and 0.3 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.
17 . The R-T-B based permanent magnetic according to claim 1 , wherein elements other than the group consisting of R, B, Co, Ga, Al, Cu, Zr, and C is Fe and inevitable impurities, and an amount of the inevitable impurities is 0 or more and 0.5 mass % or less with respect to 100 mass % of the R-T-B based permanent magnet as a whole.