Tdk Corporation

Other

Chikara Ishizaka

Eiji Kato

Yoshinori Fujikawa

Tetsuya Hidaka

Taeko Tsubokura

Gouichi Nishizawa

Katsuo Sato

Akira Fukuno

Makoto Iwasaki

Masashi Miwa

Fumitaka Baba

Haruna Nakajima

Yasushi Enokido

Yuki Nagamine

Tamotsu Ishiyama

Wakako Okawa

Nobuhiro Jingu

Tsutomu Chou

Satoshi Tanaka

Takeshi Masuda

Jun Hagiwara

Koji Mitake

Nobuya Uchida

Ken-ichi Nishikawa

Masahiro Ito

Taku Takeishi

Masao Shigeta

Takuma Hayakawa

Syota Goto

Katsuhiko Wakayama

Naoto Tsukamoto

Makoto Nakane

Masahiro Karatsu

Ayato Kakoki

Shohei Mimura

Takahiro Kawashima

Masatoshi Hatakeyama

Mari Fujii

Katsumi Saito

Hiroshi Miyasaka

Atsushi Fujiwara

The present invention provides a rare earth based magnet that inhibits the high temperature demagnetization rate even when less or no heavy rare earth elements such as Dy, Tb and the like are used. The rare earth based magnet according to the present invention includes RTB main phase crystal grains and grain boundary phases between adjacent main phase crystal grains. In any cross-section of the rare earth based magnet, when evaluating the circular degree of the main phase crystal grains with Wadell's Roundness A, the shape of the main phase crystal grains is controlled such that the Roundness A becomes 0.24 or more.

Rare earth based magnet

An R-T-B based sintered magnet includes a first main surface and a first side surface. The first main surface has a coercivity that is higher than that of the first side surface. &#x394;Hcj&#x2264;60 kA/m is satisfied, where &#x394;Hcjis a difference in coercivity between a portion having a highest coercivity on the first main surface and a portion having a lowest coercivity on the first main surface. &#x394;Hcj&#x2264;60 kA/m is satisfied, where &#x394;Hcjis a difference in coercivity between a portion having a highest coercivity on a first cross section and a portion having a lowest coercivity on the first cross section and the first cross section is a cross section parallel to the first main surface and spaced from the first main surface at a predetermined length or more.

R-T-B based sintered magnet and motor

A motor includes a magnet and a coil. &#x3b1;2=[{(Br2&#x2212;Br1)/Br1}/(T2&#x2212;T1)]&#xd7;100&#x2265;&#x2212;0.10 and &#x3b1;3=[{(Br3&#x2212;Br1)/Br1}/(T3&#x2212;T1)]&#xd7;100&#x2264;&#x2212;0.12 are satisfied. In the magnet, Br1 (mT) is a residual magnetic flux density at T1 (&#xb0; C.), Br2 (mT) is a residual magnetic flux density at T2 (&#xb0; C.), and Br3 (mT) is a residual magnetic flux density at T3 (&#xb0; C.), and &#x3b1;2 (%/&#xb0; C.) is a temperature coefficient at a target temperature of T2 (&#xb0; C.) with respect to a reference temperature of T1 (&#xb0; C.), and &#x3b1;3 (%/&#xb0; C.) is a temperature coefficient at a target temperature of T3 (&#xb0; C.) with respect to a reference temperature of T1 (&#xb0; C.) in conditions of T1=23, T2=60, and T3=180.

Motor

The present invention provides a rare earth based magnet in which the demagnetization rate at a high temperature can be inhibited even if the amount of heavy rare earth element(s) such as Dy and Tb is evidently decreased compared to the past or no such heavy rare earth element is used. The rare earth based magnet of the present invention is a sintered magnet which comprises RTB crystal grains as the main phases and the crystal boundary phases among the RTB crystal grains. The microstructure of the sintered body is controlled by including crystal boundary phases containing at least R, T and M in the crystal boundary phases, wherein the relative atomic ratios of R, T and M are as follows, i.e., 25 to 35% for R, 60 to 70% for T and 2 to 10% for M.

Provided is a sintered magnet that is an R-T-B based sintered magnet having a region having a concentration of at least one heavy rare earth element decreasing from the surface toward the inside, in which the at least one heavy rare earth element includes at least either of Tb or Dy, R includes Nd, T includes Fe, Co, and Cu, there is a grain boundary phase containing at least either of Tb or Dy and Nd between two main phase particles, and a value obtained by subtracting a half value width of a concentration distribution curve of Cu from a half value width of a concentration distribution curve of Tb or Dy in a part including the grain boundary phase is from 10 to 20 nm.

Alloy for R-T-B based sintered magnet and R-T-B based sintered magnet

The present invention provides a rare earth based magnet that inhibits the high temperature demagnetization rate even when less or no heavy rare earth elements such as Dy, Tb and the like than before are used. The rare earth based magnet according to the present invention is a sintered magnet which includes RTB crystal grains as main phase and grain boundary phases between the RTB crystal grains. When the grain boundary phase surrounded by three or more main phase crystal grains is regarded as the grain boundary multi-point, the microstructure of the sintered body is controlled so that the ratio of the grain boundary triple-point surrounded by three main phase crystal grains in all grain boundary multi-points to be specified value or less.

An R-T-B based sintered magnet having RTB crystal grains and a grain boundary formed by two or more adjacent RTB crystal grains. An R&#x2014;Co&#x2014;Cu&#x2014;N concentrated part whose concentrations of R, Co, Cu and N are respectively higher than those in the RTB crystal grains may be in the grain boundary. An R&#x2014;O&#x2014;C concentrated part or an R&#x2014;O&#x2014;C&#x2014;N concentrated part may be further provided in the grain boundary.

R-T-B based sintered magnet

The present invention provides a rare earth based magnet including RTB main-phase crystal grains, and two-grain boundary phases between adjacent two RTB 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.

The present invention provides a rare earth based magnet in which the demagnetization rate at a high temperature can be inhibited even if the amount of heavy rare earth element(s) such as Dy and Tb is evidently decreased compared to the past or no such heavy rare earth element is used. The rare earth based magnet of the present invention is a sintered magnet which comprises RTB crystal grains as the major phases and the crystal boundary phases among the RTB crystal grains. The microstructure of the sintered body is controlled by including crystal boundary phases containing at least R, T and M in the crystal boundary phases, wherein the relative atomic ratios of R, T and M are as follows, i.e., 60 to 80% for R, 15 to 35% for T and 1 to 20% for M.

The present invention provides a rare earth based magnet in which the demagnetization rate at a high temperature can be inhibited even if the amount of heavy rare earth element(s) such as Dy and Tb is evidently decreased compared to the past or no such heavy rare earth element is used. The rare earth based magnet of the present invention is a sintered magnet which comprises RTB crystal grains as the main phases and the crystal boundary phases among RTB crystal grains. The microstructure of the sintered body is controlled by at least containing the first crystal boundary phases and the second crystal boundary phases, wherein the first crystal boundary phases contain at least R-T-M in the ranges of 20 to 40 atomic % for R, 60 to 75 atomic % for T and 1 to 10 atomic % for M, and the second crystal boundary phases contains at least R-T-M in the ranges of 50 to 70 atomic % for R, 10 to 30 atomic % for T and 1 to 20 atomic % for M.

The present invention provides a rare earth based magnet that inhibits the high temperature demagnetization rate even when less or no heavy rare earth elements such as Dy, Tb and the like than before are used. The rare earth based magnet according to the present invention is a sintered magnet which includes RTB crystal grains as main phase and grain boundary phases between the RTB crystal grains. when evaluating the cross-sectional area distribution of the main phase crystal grains by histogram in any cross-section of the rare earth based magnet, the crystal grains with large particle size and the crystal grains with small particle size are controlled so that the cross-sectional area distribution becomes the one which respectively has at least one peak at two sides of the average value of the cross-sectional area.

A sintered magnet of a preferred embodiment has a composition comprising: R (R is a rare earth element that must contain any one of Nd and Pr.): 29.5 to 33.0 mass %; B: 0.7 to 0.95 mass %; Al: 0.03 to 0.6 mass %; Cu: 0.01 to 1.5 mass %; Co: 3.0 mass % or less (provided that 0 mass % is not included.); Ga: 0.1 to 1.0 mass %; C: 0.05 to 0.3 mass %; O: 0.03 to 0.4 mass %; and Fe and other elements: a balance, and wherein a content of heavy rare earth elements in total is 1.0 mass % or less, and wherein the following relations are satisfied: 0.29&#x3c;[B]/([Nd]+[Pr])&#x3c;0.40 and 0.07&#x3c;([Ga]+[C])/[B]&#x3c;0.60, where [Nd], [Pr], [B], [C] and [Ga] represent the numbers of atoms of Nd, Pr, B, C and Ga, respectively.

Sintered magnet

The present invention provides an R-T-B based sintered magnet including RTB crystal grains wherein; a grain boundary is formed by two or more adjacent RTB crystal grains, an R&#x2014;O&#x2014;C concentrated part, in which concentrations of R, O and C are higher than those in the RTB crystal grains respectively, is in the grain boundary, and a ratio (O/R) of O atom to R atom in the R&#x2014;O&#x2014;C concentrated part satisfies the following formula (1):0.4&#x3c;(O/R)&#x3c;0.7.

An R-T-B based alloy strip including columnar crystals of an RTB phase, wherein in a cross-section along the thickness direction, columnar crystals extend out in a radial fashion from the crystal nuclei, the R-T-B based alloy strip satisfying the following inequality (1), where Dand Dare, respectively, the average value for the lengths of the columnar crystals on one side and the average value for the lengths on the other side that is opposite the one side, in the direction perpendicular to the thickness direction of the cross-section.0.9/1.1&#x2266;&#x2266;1.1/0.9&#x2003;&#x2003;(1)

R-T-B based alloy strip, and R-T-B based sintered magnet and method for producing same

An R-T-B sintered magnet including a composition containing a rare earth element, a transition element and boron, containing essentially no dysprosium as a rare earth element, and having crystal grains with a composition containing a rare earth element, a transition element and boron, and grain boundary regions formed between the crystal grains, wherein the triple point regions which are grain boundary regions surrounded by 3 or more crystal grains have a composition containing a rare earth element, a transition element and boron and have a higher mass ratio of the rare earth element than the crystal grains, the average value of the area of the triple point regions in a cross-section being no greater than 2 &#x3bc;mand the standard deviation of the area distribution being no greater than 3.

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Tokyo, Japan

Chikara Ishizaka