Rare earth magnet, method for manufacturing the same, and motor using rare earth magnet

Abstract

A rare earth magnet has a sintered body including: rare earth magnet particles; and a rare earth oxide being present between the rare earth magnet particles, the rare earth oxide being represented by a following general formula (I): R 2 O 3   (I) where R is any one of terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. The rare earth magnet particle is constituted by a cluster of numerous crystal grains, and an electric resistivity of the rare earth magnet is within a range from 26.0 to 75.0 μΩm.

1 . A rare earth magnet, comprising: 
 a sintered body including: rare earth magnet particles; and a rare earth oxide being present between the rare earth magnet particles, the rare earth oxide being represented by a following general formula (I):      R 2 O 3    (I)    where R is any one of terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium,    wherein the rare earth magnet particle is constituted by a cluster of numerous crystal grains, and    an electric resistivity of the rare earth magnet is within a range from 26.0 to 75.0 μΩm.    
   
   
       2 . The rare earth magnet of  claim 1 , 
 wherein the electric resistivity is within a range from 26.0 to 35.0 μΩm.    
   
   
       3 . The rare earth magnet of  claim 1 , 
 wherein the rare earth magnet is a Nd—Fe—B type magnet.    
   
   
       4 . The rare earth magnet of  claim 1 , 
 wherein the rare earth magnet is an anisotropic magnet.    
   
   
       5 . The rare earth magnet of  claim 1 , 
 wherein a size of the rare earth magnet particle is in a range from 1 μm to 500 μm inclusive, and a size of the crystal grain is 500 nm or below.    
   
   
       6 . The rare earth magnet of  claim 1 , 
 wherein a size of the crystal grain is not greater than a single-domain critical gram size.    
   
   
       7 . The rare earth magnet of  claim 1 , further comprising: 
 a protective film provided on a surface of the rare earth magnet.    
   
   
       8 . The rare earth magnet of  claim 1 , 
 wherein a content of the rare earth oxide in the rare earth magnet is within a range from 0.1 mass % to 20 mass %.    
   
   
       9 . The rare earth magnet of  claim 8 , 
 wherein the content is within a range from 1 mass % to 5 mass %.    
   
   
       10 . A rare earth magnet, comprising: 
 a sintered body including: rare earth magnet particles; and a rare earth oxide being present only between the rare earth magnet particles, the rare earth oxide being represented by a following general formula (I):      R 2 O 3    (I)    where R is any one of terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium,    wherein the rare earth magnet particle is constituted by a cluster of numerous crystal grains.    
   
   
       11 . The rare earth magnet of  claim 10 , 
 wherein the rare earth magnet is a Nd—Fe—B type magnet.    
   
   
       12 . The rare earth magnet of  claim 10 , 
 wherein the rare earth magnet is an anisotropic magnet.    
   
   
       13 . The rare earth magnet of  claim 10 , 
 wherein a size of the rare earth magnet particle is in a range from 1 μm to 500 μm inclusive, and a size of the crystal grain is 500 nm or below.    
   
   
       14 . The rare earth magnet of  claim 10 , 
 wherein a size of the crystal grain is not greater than a single-domain critical grain size.    
   
   
       15 . The rare earth magnet of  claim 10 , further comprising: 
 a protective film provided on a surface of the rare earth magnet.    
   
   
       16 . The rare earth magnet of  claim 10 , 
 wherein an electric resistivity of the rare earth magnet is within a range from 26.0 to 75.0 μΩm.    
   
   
       17 . The rare earth magnet of  claim 16 , 
 wherein the electric resistivity is within a range from 26.0 to 35.0 μΩm.    
   
   
       18 . The rare earth magnet of  claim 10 , 
 wherein a content of the rare earth oxide in the rare earth magnet is within a range from 0.1 mass % to 20 mass %.    
   
   
       19 . The rare earth magnet of  claim 18 , 
 wherein the content is within a range from 1 mass % to 5 mass %.    
   
   
       20 . A motor, comprising: 
 a rare earth magnet comprising a sintered body having rare earth magnet particles and a rare earth oxide being present between the rare earth magnet particles, the rare earth oxide being represented by a following general formula (I):      R 2 O 3    (I)    where R is any one of terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium,    wherein the rare earth magnet particle is constituted by a cluster of numerous crystal grains, and    an electric resistivity of the rare earth magnet is within a range from 26.0 to 75.0 μΩm.    
   
   
       21 . The motor of  claim 20 , 
 wherein the electric resistivity is within a range from 26.0 to 35.0 μΩm.    
   
   
       22 . The motor of  claim 20 , 
 wherein a size of the rare earth magnet particle is in a range from 1 μm to 500 μm inclusive, and a size of the crystal grain is 500 nm or below.    
   
   
       23 . The motor of  claim 20 , 
 wherein a size of the crystal grain is not greater than a single-domain critical grain size.    
   
   
       24 . The motor of  claim 20 , 
 wherein the rare earth magnet is coated with a protective film.    
   
   
       25 . A motor, comprising: 
 a rare earth magnet comprising a sintered body having rare earth magnet particles and a rare earth oxide being present only between the rare earth magnet particles, the rare earth oxide being represented by a following general formula (I):      R 2 O 3    (I)    where R is any one of terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium,    wherein the rare earth magnet particle is constituted by a cluster of numerous crystal grains.    
   
   
       26 . The motor of  claim 25 , 
 wherein a size of the rare earth magnet particle is in a range from 1 μm to 500 μm inclusive, and a size of the crystal grain is 500 nm or below.    
   
   
       27 . The motor of  claim 25 , 
 wherein a size of the crystal grain is not greater than a single-domain critical gram size.    
   
   
       28 . The motor of  claim 25 , 
 wherein the rare earth magnet is coated with a protective film.    
   
   
       29 . The motor of  claim 25 , 
 wherein an electric resistivity of the rare earth magnet is within a range from 26.0 to 75.0 μΩm.    
   
   
       30 . The motor of  claim 29 , 
 wherein an electric resistivity of the rare earth magnet is within a range from 26.0 to 35.0 μΩm.    
   
   
       31 . A method of manufacturing a rare earth magnet, comprising: 
 forming a rare earth magnet particle constituted by a cluster of numerous crystal grains,    preparing a mixture including the rare earth magnet particle and a rare earth oxide being represented by a following general formula (I):      R 2 O 3    (I)    where R is any one of terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium;    filling the mixture in a molding die; and    molding the mixture at a temperature of 600° C. to 850° C.    
   
   
       32 . The method of manufacturing a rare earth magnet of  claim 31 , further comprising: 
 between the filling and the molding, pre-molding the mixture while the rare earth magnet powder being subjected to magnetic field orientation,    wherein the rare earth magnet particle is anisotropic magnet.    
   
   
       33 . The method of manufacturing a rare earth magnet of  claim 31 , 
 wherein the molding is a step which molds the mixture by pressure sintering.    
   
   
       34 . The method of manufacturing a rare earth magnet of  claim 31 , 
 wherein the rare earth magnet particle is formed by HDDR method or UPSET method.    
   
   
       35 . The method of manufacturing a rare earth magnet of  claim 31 , 
 wherein a size of the rare earth magnet particle is in a range from 1 μm to 500 μm inclusive, and a size of the crystal grain is 500 nm or below.    
   
   
       36 . The method of manufacturing a rare earth magnet of  claim 31 , 
 wherein the preparing the mixture is performed by MOCVD method.