Rare earth based magnet
The present invention provides a rare earth based magnet including R 2 T 14 B main-phase crystal grains, and two-grain boundary phases between adjacent two R 2 T 14 B main-phase crystal grains, the two-grain boundary phases are controlled such that the thickness thereof is 5 nm or more and 500 nm or less, and it is composed of a phase with a magnetism different from that of a ferromagnet.
1. A rare earth based magnet comprising:
R 2 T 14 B main-phase crystal grains, where R is at least one element selected from the group consisting of rare earth elements, and T is Fe or the combination of Fe and Co,
the rare earth based magnet contains M and Cu,
M is at least one element selected from the group consisting of Al, Ge, Si, Sn, and Ga,
contents of the elements relative to the total mass are shown as follows:
R: 30.5 to 33 mass %,
B: 0.7 to 0.92 mass %,
M: 0.2 to 1.5 mass %,
Cu: 0.1 to 0.7 mass %, and
Fe: balance, substantially, and
the total content of elements other than Fe occupying the balance: 5 mass % or lower,
the content of heavy rare earth elements in total mass of the sintered magnet is 0.1 mass % or less, and
two-grain boundary phases between adjacent two R 2 T 14 B main-phase crystal grains,
wherein the two-grain boundary phases have an average thickness of the two-grain boundary phases in any section with respect to all measuring points in a range of 5 nm or more and 490 nm or less,
the thickness of the two-grain boundary phases is the thickness evaluated via HRTEM,
the measuring points are points in which three points are present on each two-grain boundary phase in any section,
the three points which are present on each two-grain boundary phase are determined by two boundaries between the two-grain boundary phase and triple junctions connecting thereto, the interval between the two boundaries is quadrisected, and when three quadrisectors are drawn, the three points are located at positions of the three quadrisectors,
a thickness of each two-grain boundary phase on which the three points are present is a distance between the two R 2 T 14 B main-phase crystal grains on the three quadrisectors,
the average thickness of the two-grain boundary phases is an average of measured values of 60 measuring points in 20 arbitrarily selected two-grain boundary phases,
at least some of the two-grain boundary phases are composed of a phase with a magnetism different from that of the R 2 T 14 B main-phase,
the two-grain boundary phases contain a rare earth element and the atomic concentration of the rare earth element in at least one of the two-grain boundary phases is 90 at % or more,
a R 6 T 13 M phase and a layer are formed in at least one of the two-grain boundary phases, the layer is a thin microcrystal layer, an amorphous layer, or a microcrystal-containing amorphous layer, and
the layer is formed in the boundary between the R 6 T 13 M phases and the R 2 T 14 B main-phase crystal grains and a thickness of the layer is 0.5 nm or more and 1/10 of the thickness of the R 6 T 13 M two-grain boundary phase or less.
2. The rare earth based magnet according to claim 1 , wherein, with respect to all measuring points, a ratio of measuring points which are composed of a phase with a magnetism different from that of the R 2 T 14 B main phase and have the two-grain boundary phases being 5 nm or more and 490 nm or less in thickness is 20% or more.
3. The rare earth based magnet according to claim 2 , wherein the R 6 T 13 M phase has a La 6 Co 11 Ga 3 crystal structure.
4. The rare earth based magnet according to claim 2 , further comprising at least two kinds of two-grain boundary phases of a first two-grain boundary phase and a second two-grain boundary phase,
wherein, in the first two-grain boundary phase the atomic concentration of rare earth element is 90 at % or more, and the second two-grain boundary phase contains the R 6 T 13 M phase with a La 6 Co 11 Ga 3 crystal structure.
5. The rare earth based magnet according to claim 1 , wherein the R 6 T 13 M phase has a La 6 Co 11 Ga 3 crystal structure.
6. The rare earth based magnet according to claim 1 , further comprising at least two kinds of two-grain boundary phases of a first two-grain boundary phase and a second two-grain boundary phase,
wherein, in the first two-grain boundary phase the atomic concentration of rare earth element is 90 at % or more, and the second two-grain boundary phase contains the R 6 T 13 M phase with a La 6 Co 11 Ga 3 crystal structure.
7. The rare earth based magnet according to claim 1 , wherein the rare earth element represents at least one selected from the group consisting of Nd and Pr.
8. The rare earth based magnet according to claim 1 , wherein
the rare earth based magnet contains O, C and N,
the content of C is 0.1 to 0.25 mass %,
the content of O is 0.05 to 0.25 mass %, and
the content of N is 0.15 mass % or less.
9. The rare earth based magnet according to claim 8 , wherein
the numbers of O, C and N atoms contained in the rare earth based magnet are referred to as [O], [C] and [N],
[O]/([C]+[N])<0.60.
10. The rare earth based magnet according to claim 1 , wherein
R represents at least one selected from Nd and Pr,
the rare earth based magnet contains C,
the numbers of Nd, Pr, B, C and M atoms contained in the rare earth based magnet are referred to as [Nd], [Pr], [B], [C] and [M],
0.27<[B]/([Nd]+[Pr])<0.40 and 0.07<([M]+[C])/[B]<0.60.
11. A rare earth based magnet comprising:
R 2 T 14 B main-phase crystal grains, where R is at least one element selected from the group consisting of rare earth elements, and T is Fe or the combination of Fe and Co, and
the rare earth based magnet contains M and Cu,
M is at least one element selected from the group consisting of Al, Ge, Si, Sn, and Ga,
contents of the elements relative to the total mass are shown as follows:
R: 30.5 to 33 mass %,
B: 0.7 to 0.92 mass %,
M: 0.2 to 1.5 mass %,
Cu: 0.1 to 0.7 mass %, and
Fe: balance, substantially, and
the total content of elements other than Fe occupying the balance: 5 mass % or lower,
the content of heavy rare earth elements in total mass of the sintered magnet is 0.1 mass % or less, and
two-grain boundary phases between adjacent two R 2 T 14 B main-phase crystal grains,
wherein the two-grain boundary phases have an average thickness of the two-grain boundary phases in any section with respect to all measuring points in a range of 5 nm or more and 490 nm or less,
the thickness of the two-grain boundary phases is the thickness evaluated via HRTEM,
the measuring points are points in which three points are present on each two-grain boundary phase in any section,
the three points which are present on each two-grain boundary phase are determined by two boundaries between the two-grain boundary phase and triple junctions connecting thereto, the interval between the two boundaries is quadrisected, and when three quadrisectors are drawn, the three points are located at positions of the three quadrisectors,
a thickness of each two-grain boundary phase on which the three points are present is a distance between the two R 2 T 14 B main-phase crystal grains on the three quadrisectors,
the average thickness of the two-grain boundary phases is an average of measured values of 60 measuring points in 20 arbitrarily selected two-grain boundary phases,
a R 6 T 13 M phase and a layer are formed in at least one of the two-grain boundary phases, the layer is a thin microcrystal layer, an amorphous layer, or a microcrystal-containing amorphous layer,
wherein the layer is formed in the boundary between the R 6 T 13 M phases and the R 2 T 14 B main-phase crystal grains and a thickness of the layer is 0.5 nm or more and 1/10 of the thickness of the R 6 T 13 M two-grain boundary phase or less.
12. The rare earth based magnet according to claim 11 , wherein
the rare earth based magnet contains O, C and N,
the content of C is 0.1 to 0.25 mass %,
the content of O is 0.05 to 0.25 mass %, and
the content of N is 0.15 mass % or less.
13. The rare earth based magnet according to claim 12 , wherein
the numbers of O, C and N atoms contained in the rare earth based magnet are referred to as [O], [C] and [N],
[O]/([C]+[N])<0.60.
14. The rare earth based magnet according to claim 11 , wherein
R represents at least one selected from Nd and Pr,
the rare earth based magnet contains C,
the numbers of Nd, Pr, B, C and M atoms contained in the rare earth based magnet are referred to as [Nd], [Pr], [B], [C] and [M],
0.27<[B]/([Nd]+[Pr])<0.40 and 0.07<([M]+[C])/[B]<0.60.