Tdk Corporation

National Institute of Advanced Industrial Science and Technology

Massachusetts Institute of Technology

Yasushi Enokido

Daisuke Tanaka

Ryuji Hashimoto

Kenichi Suzuki

Chikara Ishizaka

Kenta Takagi

Akihiro Ohsawa

Shusuke Okada

Yoshinori Fujikawa

Kyung-Ku Choi

Gouichi Nishizawa

Ryo Yokoyama

Takeshi Masuda

Hitoshi Saita

Isao Nakahata

Kimihiro Ozaki

Naoyoshi Sato

Fumitaka Baba

Tomohiro Sogabe

Kenichi Nishikawa

Hironori Wada

Kazuyuki Suzuki

Ikuya Kokawa

The rare-earth-based magnet powder has an average value of 0.65 or more as sphericity P1 defined by an equation (1) of P1=Ls/Ll. In the equation (1), Ll is a length or a long side of a rectangle that circumscribes the rare-earth-based magnet powder in a photomicrograph so that an area of the rectangle is minimized, and Ls is a length of a short side of the rectangle that circumscribes the rare-earth-based magnet powder in the photomicrograph so that the area of the rectangle is minimized.

Rare-earth-based magnet powder, bonded magnet, bonded magnet compound, sintered magnet, method of manufacturing rare-earth-based magnet powder, and method of manufacturing rare-earth based permanent magnet

One embodiment of the present invention includes, in a samarium-iron-nitrogen based magnet powder, a main phase containing samarium and iron, and a sub-phase containing samarium, iron, and at least one or more elements selected from the group consisting of zirconium, molybdenum, vanadium, tungsten, and titanium, wherein an atomic ratio of a rare earth element to an iron group element is greater than an atomic ratio of the rare earth element to the iron group element of the main phase, wherein at least a part of a surface of the main phase is coated with the sub-phase.

Samarium-iron-nitrogen based magnet powder and method of manufacturing same, and samarium-iron-nitrogen based magnet and method of manufacturing same

A samarium-iron-nitrogen alloy powder according to one embodiment of the present invention is characterized in that a value obtained by dividing the hydrogen content of the samarium-iron-nitrogen alloy powder by the BET specific surface area of the samarium-iron-nitrogen alloy powder is less than or equal to 400 ppm/(m/g), and a value obtained by dividing the oxygen content of the samarium-iron-nitrogen alloy powder by the BET specific surface area of the samarium-iron-nitrogen alloy powder is less than or equal to 11,000 ppm/(m/g).

Samarium-iron-nitrogen alloy powder and method for producing same

One embodiment of the present invention is that in samarium-iron-nitrogen magnet powder, a non-magnetic phase is formed on a surface of the samarium-iron-nitrogen magnet phase, and an arithmetic mean roughness Ra of the surface is 3.5 nm or less.

Samarium-iron-nitrogen magnet powder and method for manufacturing same

A rare earth based permanent magnet formed by a sintered compact with an R-T-B based composition, wherein, R contains R1 and R2 as the necessity, R1 represents at least one rare earth element including Y and excluding Dy, Tb and Ho, and R2 represents at least one from the group made of Dy, Tb and Ho. Its main phase grains have a core-shell structure in which a core part and shell part coating the core part are contained. When the atom concentrations of R1 and R2 in the core part and the atom concentrations of R1 and R2 in the shell part are defined as &#x3b1;R1, &#x3b1;R2, &#x3b2;R1 and &#x3b2;R2, respectively, &#x3b1;R1&#x3c;&#x3b2;R1, &#x3b1;R2&#x3e;&#x3b2;R2, &#x3b1;R1&#x3c;&#x3b1;R2 and &#x3b2;R2&#x3c;&#x3b2;R1. Relative to all the main phase grains observed at the cross-section of the sintered compact, the ratio occupied by the main phase grain having the core-shell structure is 5% or more.

Rare earth based permanent magnet

A rare earth based permanent magnet has a sintered compact with R-T-B based composition. The compact has two kinds of main phase grains M1 and M2 having different concentration distributions of R including R1 and R2 respectively representing at least one rare earth element including Y and excluding Dy, Tb and Ho, and at least one from Ho, Dy and Tb. M1 and M2 have a core-shell structure containing a shell part coating a core part. In M1, when the R1 and R2 atom concentrations in the core and shell parts are defined as &#x3b1;R1, &#x3b1;R2, &#x3b2;R1 and &#x3b2;R2, respectively, &#x3b1;R1&#x3e;&#x3b2;R1, &#x3b1;R2&#x3c;&#x3b2;R2, &#x3b1;R1&#x3e;&#x3b1;R2 and &#x3b2;R1&#x3c;&#x3b2;R2. In M2, when the R1 and R2 atom concentrations in the core and shell parts are defined as &#x3b3;R1, &#x3b3;R2, &#x3b5;R1 and &#x3b5;R2, respectively, &#x3b3;R1&#x3c;&#x3b5;R1, &#x3b3;R2&#x3e;&#x3b5;R2, &#x3b3;R1&#x3c;&#x3b3;R2 and &#x3b5;R1&#x3e;&#x3b5;R2. Ratios occupied by the main phase grains having the core-shell structure are 5% or more, respectively.

The present invention provides a permanent magnet with both a high corrosion resistance and magnetic properties compared to the existing R-T-B based magnets. It is a R-T-B based sintered magnet (wherein, R includes Y (yttrium) and R1 as essential, R1 is at least one kind of rare earth elements except Y but includes Nd as essential, and T is at least one kind of transition metal element including Fe or the combination of Fe and Co as essential). By allowing the ratio of R1 to Y (R1:Y) in the R contained in the grain boundary phase to be 80:20&#x2dc;35:65 in terms of the calculated molar ratio of the grain boundary phase and adding Y to the raw materials of the R-T-B based magnet, Y segregates at the triple point, and corrosion of grain boundary phase is prevented by oxidized Y.

R&#x2014;T&#x2014;B based sintered magnet

The present invention provides a R-T-B based permanent magnet, comprising a demagnetization curve having a slope &#x394;J/&#x394;(H/HcJ) of less than 400 kG at a region where the value of magnetic field is Hk or less, wherein it is preferable that R in the composition of R-T-B is represented by (R1R2), and T represents one or more transition metal elements containing Fe or a combination of Fe and Co as necessary, where: R1 represents the rare earth element(s) composed of one or more elements selected from the group consisting of Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and R2 contains at least one element selected from the group consisting of Y, Ce and La, and 0.2&#x2264;x&#x2264;0.7.

R-T-B based permanent magnet

An R-T-B based permanent with the residual magnetic flux density Br2 satisfies the relationship of Br2/Br&#x2265;0.90, wherein the residual magnetic flux density Br2 is obtained after applying the external magnetic field of Hex and then applying an external magnetic field of 0.95 HcJ. Such a R-T-B based permanent magnet preferably contains main phase grains with a composition of (R1R2)TB (R1 is rare earth element(s) composed of one or more elements selected from the group consisting of Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, R2 is element(s) containing at least one selected from the group consisting of Y, La and Ce, T is one or more transition metal elements including Fe or a combination of Fe and Co as essential elements, and 0.2&#x2264;x&#x2264;0.7) and thus can be suitably used as a magnet with a variable magnetic force for a variable magnetic flux motor.

The present invention provides an R-T-B based permanent magnet suitable as a magnet with a variable magnetic force for a motor with variable magnetic flux, which has a high residual magnetic flux density, a low coercivity, and a magnetic force that can be reversibly varied by a small external magnetic field. A permanent magnet with a high residual magnetic flux density and a low coercivity that is suitable as a variable magnet for a motor with variable magnetic flux can be obtained, by selecting the rare earth elements consisting of one or more of Y, La and Ce for a predetermined amount of the rare earth element(s) R in the R-T-B based permanent magnet, and further adding a predetermined amount of the additive element(s) which is at least one of Al, Cu, Zr, Hf and Ti.

R-T-B based permanent magnet and rotating machine

In the present invention, a permanent magnet with excellent temperature properties and magnetic properties which will not significantly deteriorate can be stably prepared, by using a raw alloy for the R-T-B based permanent magnet in which the rare earth element(s) composed of at least one selected from the group consisting of Y, La and Ce is selected as a predetermined amount of the rare earth element R in the R-T-B based permanent magnet and a proper amount of Ca is contained.

R-T-B based permanent magnet and raw alloy for the same

The present invention provides a permanent magnet suitable as a variable flux magnet for a variable magnetic flux motor. A permanent magnet comprising R (R is composed of 75 at % or more of Nd and 25 at % or less of at least one element selected from the group consisting of Y, Ce, La, Pr, Sm, Eu, Gd, Er, Tm, Yb and Lu), Fe and B as the main component, wherein, said permanent magnet is composed of a main phase of a crystal structure represented by RFeB, a ratio of the element R to all constituent element satisfies 11.8 at %&#x2266;R&#x2266;12.2 at %, a cross-sectional area ratio Are of the sub-phase with a higher concentration of R than that of the main phase to the whole magnet structure satisfies 0%&#x3c;Are&#x2266;1.3%, and a cross-sectional area ratio Ama of the main phase to the whole magnet structure is 97%&#x2266;Ama.

Permanent magnet and variable magnetic flux motor

The present invention provides an R-T-B based permanent magnet, comprising: a main phase which is composed of the structure of RTB (R is at least one element selected from Y, La, Ce, Pr, Nd, Sm, Eu and Gd, and T is one or more transition metal elements having Fe or a combination of Fe and Co as necessary); and a grain boundary phase which is composed of CeM(M is at least one element selected from Mg, Al, Si, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Ag, In, Sn, La, Pr, Nd, Sm, Eu, Gd, Hf, Ta, W and Bi, and x is within the range of 0.20&#x2266;x&#x2266;0.55), and the cross-sectional ratio Atre of the grain boundary phase to the whole magnet structure is within the range of 0.03&#x3c;Atre&#x3c;0.07.

Permanent magnet and motor

A magnet powder having a composition composed of R (R consists of R1 and R2, R1 represents at least one rare earth element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Er, Tm, Yb and Lu, R2 represents at least one rare earth element selected from the group consisting of Ho and Gd). T (T represents at least one transition metal element containing Fe or the combination of Fe and Co as essential element(s)) and B, wherein, the atomic ratio of R2/(R1&#xd7;R2) is 0.05 to 0.1, the ratio of R/T is 0.25 to 0.35, and the magnet powder has an average primary particle size of 45 to 100 nm. The present invention also provides a bond magnet using the magnet powder.

Magnet powder, bond magnet and motor

The present invention provides a permanent magnet with a coercivity that will not be significantly decreased and a light weight compared to conventional R-T-B based permanent magnets. A core-shell structure is formed for the major phase grain by adding Cu to the R-T-B based magnet which is the raw material. When the mass concentration of Y in the core portion is set as EY, the mass concentration of Y in the shell portion is set as LY and the mass concentration of Y in the R&#x2014;Fe&#x2014;B crystal grain calculated from the ratio R1:Y in the total composition is set as SY, the ratio &#x3b1; of EY to SY (EY/SY) is 1.1 or more. Thus, the magnetic insulation among the crystal grains becomes better which prevents the coercivity from decreasing due to the addition of Y. Further, the addition of Y makes the magnet lighter in weight.

Growing community of inventors

Tokyo, Japan

Yasushi Enokido