Tdk Corporation

Masashi Miwa

Haruna Nakajima

Yoshinori Fujikawa

Takurou Iwasa

Eiji Kato

Chikara Ishizaka

Katsuto Nagano

Yukihiko Shirakawa

Jun Hagiwara

Isao Kanada

Koji Miura

Taeko Tsubokura

Takeshi Sakamoto

Yoshihiko Yano

Hiroyuki Ono

Tetsuya Hidaka

Yoshitomo Tanaka

Yuki Nagamine

Masami Mori

Tamotsu Ishiyama

Koji Mitake

Ken-ichi Nishikawa

Takashi Watanabe

Masahiro Oishi

Yasuyuki Kawanaka

Mariko Fujiwara

Atsushi Fujiwara

To provide an R-T-B based permanent magnet having a high residual magnetic flux density Br at room temperature and a high coercivity HcJ at high temperature. In the R-T-B based permanent magnet, R is a rare earth element, T is an iron group element, and B is boron, and the R-T-B based permanent magnet includes a light rare earth element and a heavy rare earth element as R. The R-T-B based permanent magnet further includes Al, Ga, and Zr. With respect to 100 mass % of the R-T-B based permanent magnet, a total content of R is 28.50 mass % to 30.25 mass % (not including 28.50 mass %), B content is 0.93 mass % to 0.98 mass %, Al content is 0.03 mass % to 0.19 mass %, Ga content is 0.03 mass % to 0.15 mass %, and Zr content is 0.30 mass % to 0.50 mass %.

R-T-B based permanent magnet and motor

Provided is a permanent magnet including a rare-earth element R (such as Nd), a transition metal element T (such as Fe), B, Zr, and Cu. The permanent magnet contains a plurality of main phase grains including Nd, T, and B, and grain boundary multiple junctions, the one grain boundary multiple junction is a grain boundary surrounded by three or more of the main phase grains, one of the grain boundary multiple junctions contains a ZrBcrystal and an R&#x2014;Cu-rich phase including R and Cu, Fe is contained in the ZrBcrystal, a total concentration of Nd and Pr in the one grain boundary multiple junction containing both the ZrBcrystal and the R&#x2014;Cu-rich phase is higher than a total concentration of Nd and Pr in the main phase grain, a concentration of Cu in the one grain boundary multiple junction containing both the ZrBcrystal and the R&#x2014;Cu-rich phase is higher than a concentration of Cu in the main phase grain, and a unit of the concentration of each of Nd, Pr, and Cu is atomic %.

R-T-B based permanent magnet

An R-T-B based permanent magnet, excellent in magnetic properties relatively reducing amount of heavy rare earth element used, wherein R represents rare earth element, T iron group element and B boron, includes main phase grains including RTB crystal phase and grain boundaries between main phase grains. Grain boundaries include R&#x2014;O&#x2014;C&#x2014;N concentrated parts where concentrations of R, O, C and N are all higher than in main phase grains. O/R(S)&#x3e;O/R(C) wherein O/R(S) represents O/R ratio (atomic ratio) in R&#x2014;O&#x2014;C&#x2014;N concentrated parts in a surface of an R-T-B based permanent magnet and O/R(C) represents O/R ratio (atomic ratio) in R&#x2014;O&#x2014;C&#x2014;N concentrated parts in a center of an R-T-B based permanent magnet. A heavy rare earth element RH is in a surface of an R-T-B based permanent magnet as R. R&#x2014;O&#x2014;C&#x2014;N concentrated parts in a surface of an R-T-B based permanent magnet have RH/R ratio (atomic ratio) of 0.2 or less.

Provided is a permanent magnet including a rare-earth element R, a transition metal element T, B, Zr, and Cu. The permanent magnet contains main phase grains including Nd, T, and B, and grain boundary multiple junctions, the grain boundary multiple junction is a grain boundary surrounded by three or more of the main phase grains, one of the grain boundary multiple junctions contains a ZrBcrystal and an R&#x2014;Cu-rich phase, a concentration of B in the grain boundary multiple junction containing both the ZrBcrystal and the R&#x2014;Cu-rich phase is from 5 to 20 atomic %, a concentration of Cu in the grain boundary multiple junction containing both the ZrBcrystal and the R&#x2014;Cu-rich phase is from 5 to 25 atomic %, and a surface layer part of the main phase grain includes at least one kind of heavy rare-earth element among Tb and Dy.

A permanent magnetincludes Nd, Fe, and B, the permanent magnetcontains a plurality of main phase grains; and grain boundaries positioned between the main phase grains, the main phase grains include Nd, Fe, and B, at least a portion of the grain boundaries contains an R'&#x2014;O&#x2014;C phase, the R&#x2032;&#x2014;O&#x2014;C phase includes a rare earth element R&#x2032;, O, and C, the concentration of each of R&#x2032;, O, and C in the R&#x2032;&#x2014;O&#x2014;C phase is higher compared to the main phase grains, the permanent magnetcomprises a surface layer portionand a central portion, the surface layer portionis positioned on the surface side of the permanent magnet, the central portionis positioned on the inner side of the permanent magnet, the proportion of the area of the R&#x2032;&#x2014;O&#x2014;C phase occupying in a cross-section of the surface layer portionis S1 %, the proportion of the area of the R&#x2032;&#x2014;O&#x2014;C phase occupying in a cross-section of the central portionis S2%, and S1 is higher than S2.

An R-T-B based permanent magnet excellent in magnetic properties relatively reduces the amount of a heavy rare earth element used. An R-T-B based permanent magnet, wherein R represents a rare earth element, T an iron group element and B boron, includes main phase grains including an RTB crystal phase and grain boundaries formed between main phase grains. Grain boundaries include R&#x2014;O&#x2014;C&#x2014;N concentrated parts where concentrations of R, O, C and N are all higher than those in main phase grains. C/R(S)&#x3e;C/R(C) is satisfied in which C/R(S) represents a C/R ratio (atomic ratio) in R&#x2014;O&#x2014;C&#x2014;N concentrated parts present in a surface of a R-T-B based permanent magnet and C/R(C) represents a C/R ratio (atomic ratio) in the R&#x2014;O&#x2014;C&#x2014;N concentrated parts present in the center of a R-T-B based permanent magnet, and a heavy rare earth element RH is included in the R-T-B based permanent magnet.

An R-T-B-based sintered magnetcontains a rare earth element R, a transition metal element T, B, Ga, and O, the sintered magnetincludes a magnet bodyand an oxidized layercovering the magnet body, the magnet bodyincludes main phase grainscontaining a crystal of RTB and a grain boundary phasepositioned between the main phase grainsand containing R, the oxidized layerincludes a plurality of oxide phasesA containing R, T, Ga, and O, the oxide phaseA satisfies the following Formulas (1) and (2) regarding the content (unit: atom %) of each element, and the oxide phaseA in the oxidized layercovers the grain boundary phasein the magnet body0.3&#x2264;[R]/[T]&#x2264;0.5&#x2003;&#x2003;(1)0.2&#x2264;[O]/([R]+[T]+[Ga]+[O])&#x2264;0.7&#x2003;&#x2003;(2)

R-T-B-based sintered magnet

An R-T-B based permanent magnet includes main phase grains composed of RTB type compound. R is a rare earth element. T is iron group element(s) essentially including Fe or Fe and Co. B is boron. An average grain size of the main phase grains is 0.8 &#x3bc;m or more and 2.8 &#x3bc;m or less. The R-T-B based permanent magnet contains at least C and Zr in addition to R, T, and B. B is contained at 0.75 mass % or more and 0.88 mass % or less. Zr is contained at 0.65 mass % or more and 5.00 mass % or less. A formula (1) of 5.0&#x2264;[B]+[C]&#x2212;[Zr]&#x2264;5.6 is satisfied, where [B] is a B content represented by atom %, [C] is a C content represented by atom %, and [Zr] is a Zr content represented by atom %.

An R-T-B based permanent magnet includes main phase grains composed of RTB type compound. R is a rare earth element. T is iron group element(s) essentially including Fe or Fe and Co. B is boron. An average grain size of the main phase grains is 0.8 &#x3bc;m to 2.8 &#x3bc;m. The R-T-B based permanent magnet contains at least C and Ga in addition to R, T, and B. B is contained at 0.71 mass % to 0.86 mass %. C is contained at 0.13 mass % to 0.34 mass %. Ga is contained at 0.40 mass % to 1.80 mass %. A formula (1) of 0.14&#x2264;[C]/([B]+[C])&#x2264;0.30 is satisfied, where [B] is a B content represented by atom %, and [C] is a C content represented by atom %.

An R-T-B based sintered magnet including main phase particles having an RTB type crystal structure. R is at least one rare earth element essentially including a heavy rare-earth element RH. T is at least one transition metal element essentially including Fe or Fe and Co. B is boron. At least one of the main phase particles includes low RH crystal phases inside the main phase particle. The low RH crystal phases include the RTB type crystal structure, wherein an RH concentration in the low RH crystal phases is relatively lower than the RH concentration in the whole main phase particles. The R-T-B based sintered magnet may satisfy r&#x2212;r&#x2265;20% when an existence ratio of the main phase particles including the low RH crystal phases in a magnet surface layer part is r(%) and the same in a magnet central part is r(%).

R-T-B based sintered magnet

An R-T-B based sintered magnet including a plural number of main phase particles having an RTB type crystal structure. R is at least one rare earth element essentially including heavy rare earth elements RH, T is at least one transition metal element essentially including Fe or Fe and Co, and B is boron. At least one of the main phase particles is a reverse core-shell main phase particle including a core part and a shell part, in which C/C&#x3e;1.0 is satisfied when a total RH concentration (at %) in the core part is defined as Cand a total RH concentration (at %) in the shell part is defined as C. An existence ratio of the reverse core-shell main phase particles is larger in a surface layer part of the magnet than in a central part of the magnet.

An R-T-B based sintered magnet including a main phase particle comprising an RTB type crystal structure. R is at least one rare earth element, T is at least one transition metal element essentially including Fe or Fe and Co, and B is boron. The R-T-B based sintered magnet includes a magnet surface layer part and a magnet central part existing inside the magnet surface layer part. A crystal orientation degree of the main phase particle in the magnet surface layer part having a magnetic pole surface is lower than the crystal orientation degree of the main phase particle in the magnet central part.

An R-T-B based permanent magnet includes main phase grains composed of RTB type compound. R is a rare earth element. T is iron group element(s) essentially including Fe or Fe and Co. B is boron. The magnet contains at least C, Ga, and M selected from Zr, Ti, and Nb in addition to R, T, and B. B is contained at 0.71 mass % to 0.88 mass %. C is contained at 0.15 mass % to 0.34 mass %. Ga is contained at 0.40 mass % to 1.40 mass %. M is contained at 0.25 mass % to 2.50 mass %. A formula (1) of 0.14&#x2264;[C]/([B]+[C])&#x2264;0.30 and a formula (2) of 5.0&#x2264;[B]+[C]&#x2212;[M]&#x2264;5.6 are satisfied, where [B], [C], and [M] are respectively a content of B, C, and M by atom %.

An R-T-B based permanent magnet includes R-T-B based compounds as main-phase crystal grains. R is a rare earth element. T is iron group element(s) essentially including Fe or Fe and Co. B is boron. A two-grain boundary is contained between the two adjacent main-phase crystal grains. An average grain size of the main-phase crystal grains is 0.9 &#x3bc;m or more and 2.8 &#x3bc;m or less. A thickness of the two-grain boundary is 5 nm or more and 200 nm or less.

An R-T-B based sintered magnet has a high coercivity even if the carbon content becomes high accompanying the micronization of the finely pulverized particles of the raw material. The R-T-B based sintered magnet includes an R-T-B based compound as main phase grains, wherein, the R-T-B based sintered magnet contains 0.1 mass % to 0.3 mass % of C, and an R&#x2014;Ga&#x2014;C concentrated part exists in the grain boundary formed between or among two or more adjacent main phase grains, and the concentrations of R, Ga and C in the R&#x2014;Ga&#x2014;C concentrated part are higher than those in the main phase grains respectively.

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Tokyo, Japan

Masashi Miwa