Shin-etsu Chemical Co., Ltd.

Tadao Nomura

Takehisa Minowa

Hiroaki Nagata

Ken Ohashi

Yoshio Tawara

Masaru Ito

Yoshiaki Shimizu

Katsushi Tokunaga

Masayuki Kamata

Yoshihiro Kubota

Hideo Kaneko

Hajime Nakamura

Koichi Hirota

Meguru Kashida

Kazuaki Sakaki

Norio Yamagata

Kazuki Otsuka

Yuuji Gouki

Provided are an anisotropic rare earth sintered magnet having a ThMn-type crystal compound as a main phase and exhibits good magnetic characteristics, and a method for producing it. The anisotropic rare earth sintered magnet has a composition of a formula (RZr)(FeCo)(MM)OC(where R is one or more kinds selected from rare earth elements and indispensably includes Sm, Mis one or more kinds of elements selected from the group consisting of V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si, Mis one or more kinds of elements selected from the group consisting of Ti, Nb, Mo, Hf, Ta, and W, and v, w, x, y, a, b, and c each satisfy 7≤v≤15 at %, 4≤w≤20 at %, 0.2≤x≤4 at %, 0.2≤y≤2 at %, 0≤a≤0.2, 0≤b≤0.5, and 0≤c≤0.9), which contains a main phase of a ThMn-type crystal compound in an amount of 80% by volume or more with the average crystal particle diameter of the main phase being 1 μm or more, which contains an R oxycarbide in the grain boundary area, and which has a density of 7.3 g/cmor more. The production method for the anisotropic rare earth sintered magnet includes grinding an alloy that contains a ThMn-type crystal compound phase but does not contain an oxycarbide, then molding it in a mode of pressure powder molding with magnetic field application thereto to give a molded article, and thereafter sintering it at a temperature of 800° C. or higher and 1400° C. or lower to form an oxycarbide in the grain boundary area.

Anisotropic rare earth sintered magnet and method for producing the same

The invention provides an anisotropic rare earth sintered magnet having an NdFeB-type compound crystal as a main phase and containing Ce, and exhibiting good magnetic characteristics, and a method for producing the same. The anisotropic rare earth sintered magnet has a composition of a formula R(FeCo)BM(where R is two or more kinds of elements selected from rare earth elements and indispensably including Nd and Ce), in which the main phase is formed of an NdFeB-type compound crystal, main phase grains such that the Ce/R' ratio in the center part of the grains (where R′ is one or more kinds of elements selected from rare earth elements and indispensably including Nd) is lower than the Ce/R′ ratio in the outer shell part thereof exist, and a Ce-containing R′-rich phase and a Ce-containing R′(Fe,Co)phase exist in the grain boundary part. The production method is for producing the anisotropic rare earth sintered magnet.

A sintered magnet body (RTMB) coated with a powder mixture of an intermetallic compound (RM, RTM, RMH), alloy (MM) or metal (M) powder and a rare earth (R) oxide is diffusion treated. The Roxide is partially reduced during the diffusion treatment, so a significant amount of Rcan be introduced near interfaces of primary phase grains within the magnet through the passages in the form of grain boundaries. The coercive force is increased while minimizing a decline of remanence.

Rare earth permanent magnets and their preparation

A method of producing a SiC single crystal includes: disposing a SiC seed crystal at a bottom part inside a graphite crucible; causing a solution containing Si, C and R (R is at least one selected from the rare earth elements inclusive of Sc and Y) or X (X is at least one selected from the group consisting of Al, Ge, Sn, and transition metals exclusive of Sc and Y) to be present in the crucible; supercooling the solution so as to cause the SiC single crystal to grow on the seed crystal; and adding powdery or granular Si and/or SiC raw material to the solution from above the graphite crucible while keeping the growth of the SiC single crystal.

Method of producing SiC single crystal

A rare earth magnet is prepared by disposing a R-T-B sintered body comprising a RTB compound as a major phase in contact with an R-M alloy powder and effecting heat treatment for causing Relement to diffuse into the sintered body. The alloy powder is obtained by quenching a melt containing Rand M. Rand Rare rare earth elements, T is Fe and/or Co, M is selected from B, C, P, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pt, Au, Pb, and Bi.

Rare earth magnet and its preparation

A rare earth sintered magnet is an anisotropic sintered body comprising NdFeB crystal phase as primary phase and having the composition RTMSiBwherein Ris a rare earth element inclusive of Sc and Y, T is Fe and/or Co, M is Al, Cu, Zn, In, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, or W, 'a' to 'e' are 12&#x2264;a&#x2264;17, 0&#x2264;c&#x2264;10, 0.3&#x2264;d&#x2264;7, 5&#x2264;e&#x2264;10, and the balance of b, wherein Dy and/or Tb is diffused into the sintered body from its surface.

Rare earth sintered magnet and making method

A rare earth permanent magnet is prepared by disposing a powdered metal alloy containing at least 70 vol % of an intermetallic compound phase on a sintered body of R&#x2014;Fe&#x2014;B system, and heating the sintered body having the powder disposed on its surface below the sintering temperature of the sintered body in vacuum or in an inert gas for diffusion treatment. The advantages include efficient productivity, excellent magnetic performance, a minimal or zero amount of Tb or Dy used, an increased coercive force, and a minimized decline of remanence.

Rare earth permanent magnet and its preparation

An R&#x2014;Fe&#x2014;B base sintered magnet having a composition of 12&#x2013;17 at % of R (wherein R stands for at least two of yttrium and rare earth elements and essentially contains Nd and Pr), 0.1&#x2013;3 at % of Si, 5&#x2013;5.9 at % of B, 0&#x2013;10 at % of Co, and the balance of Fe, containing a R(Fe,(Co),Si)B intermetallic compound primary phase and at least 1% by volume of an R&#x2014;Fe(Co)&#x2014;Si grain boundary phase, and being free of a B-rich phase exhibits a coercive force of at least 10 kOe despite a reduced content of heavy rare earth.

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Echizen, Japan

Tadao Nomura