R-T-B based permanent magnet

1. An R-T-B based permanent magnet comprising main phase grains comprising an R 2 T 14 B compound and a grain boundary, wherein

R is one or more rare earth elements comprising Nd, T is Fe or Fe and Co, and B is boron,

the R-T-B based permanent magnet further comprises X, Z and M,

X is one or more selected from the group consisting of Ti, V, Zr, Nb, Hf and Ta, Z is one or more selected from the group consisting of C and N, M comprises Ga and further comprises one or more selected from the group consisting of Al, Si, Ge, Cu, Bi and Sn, and

the grain boundary comprises an XZ phase having a face-centered cubic structure, a crystal phase having a La 6 Co 11 Ga 3 crystal structure, an R-rich phase, an R-O-C-N phase and a body-centered cubic lattice phase, and

S 1> S 2,

S 1> S 3,

S 1> S 4 and,

S 1> S 5

wherein an area ratio of the crystal phase having a La 5 Co 11 Ga 3 crystal structure in a cross-sectional area of the R-T-B based permanent magnet is S1, an area ratio of the R-rich phase is S2, an area ratio of the R-O-C-N phase is S3, an area ratio of the body-centered cubic lattice phase is S4, and an area ratio of the XZ phase is S5, and

S1 is 7.9% or less and S3 is 2.0% or more.

2. The R-T-B based permanent magnet according to claim 1 , wherein

R content is 13.3 at % or more and 15.5 at % or less,

M content is 0.5 at % or more and 5.0 at % or less,

B content is 4.0 at % or more and 5.5 at % or less,

X content is 0.05 at % or more and 0.5 at % or less, and

T is a substantial balance,

with respect to 100 at % of the total contents of the respective elements of R, T, B, M and X, and

the R-T-B based permanent magnet further satisfies all the following expressions:

4.5< T/R< 7.0,

14< T/B< 18 and

2.5< R/B< 3.0.

3. The R-T-B based permanent magnet according to claim 1 , wherein

the maximum area of the XZ phase is 16 μm 2 or less.

4. The R-T-B based permanent magnet according to claim 2 , wherein

the maximum area of the XZ phase is 16 μm 2 or less.

5. The R-T-B based permanent magnet according to claim 1 , wherein

the maximum area of the XZ phase is 12 μm 2 or less.

6. The R-T-B based permanent magnet according to claim 2 , wherein

the maximum area of the XZ phase is 12 μm 2 or less.

7. The R-T-B based permanent magnet according to claim 1 , wherein

an existence ratio of Zr included in the XZ phase is 50 at % or more with the X being 100 at %, and

an existence ratio of C included in the XZ phase is 50 at % or more with the Z being 100 at %.

8. The R-T-B based permanent magnet according to claim 2 , wherein

an existence ratio of Zr included in the XZ phase is 50 at % or more with the X being 100 at %, and

an existence ratio of C included in the XZ phase is 50 at % or more with the Z being 100 at %.

9. The R-T-B based permanent magnet according to claim 1 , wherein

an area ratio of the XZ phase in a region of a cross-sectional area of the R-T-B based sintered magnet is 0.1 to 2%.

10. The R-T-B based permanent magnet according to claim 2 , wherein

an area ratio of the XZ phase in a region of a cross-sectional area of the R-T-B based sintered magnet is 0.1 to 2%.

11. The R-T-B based permanent magnet according to claim 1 , wherein

the crystal phase comprises R, M, B and X, and in the crystal phase,

R content is 27.0 at % or more and 32.0 at % or less,

M content is 3.0 at % or more and 8.0 at % or less,

B content is zero at % or more and 0.40 at % or less, and

X content is zero at % or more and 0.45 at % or less.

12. The R-T-B based permanent magnet according to claim 2 , wherein

the crystal phase comprises R, M, B and X, and in the crystal phase,

R content is 27.0 at % or more and 32.0 at % or less,

M content is 3.0 at % or more and 8.0 at % or less,

B content is zero at % or more and 0.40 at % or less, and

X content is zero at % or more and 0.45 at % or less.