R-t-b based sintered magnet

Abstract

An R-T-B based sintered magnet according to the present invention comprises: 12 at % to 17 at % of a rare-earth element R; 5.0 at % to 8.0 at % of boron B; 0.02 at % to 0.2 at % of Mn; and a transition metal T as the balance. The rare-earth element R is at least one element selected from the rare-earth elements, including Y (yttrium), and includes 0.2 at % to 8 at % of Pr. And the transition element T includes Fe as its main element.

1 . An R-T-B based sintered magnet having a composition comprising:
 12 at % to 17 at % of a rare-earth element R;   5.0 at % to 8.0 at % of boron B;   0.02 at % to less than 0.2 at % of Mn; and   a transition metal T as the balance,   wherein the rare-earth element R is at least one element selected from the rare-earth elements, including Y (yttrium), and includes 0.2 at % to 8 at % of Pr, and   wherein the transition metal T includes Fe as its main element.   
     
     
         2 . The R-T-B based sintered magnet of  claim 1 , wherein the magnet includes at least one of Tb and Dy as the rare-earth element R. 
     
     
         3 . The R-T-B based sintered magnet of  claim 1 , wherein the magnet includes 20 at % or less of Co as the transition metal T. 
     
     
         4 . An R-T-M-B based sintered magnet having a composition comprising:
 12 at % to 17 at % of a rare-earth element R;   5.0 at % to 8.0 at % of boron B;   0.02 at % to less than 0.2 at % of Mn;   more than 0 at % to 5.0 at % of an additive element M; and   a transition metal T as the balance,   wherein the rare-earth element R is at least one element selected from the rare-earth elements, including Y (yttrium), and includes 0.2 at % to 8 at % of Pr, and   wherein the transition metal T includes Fe as its main element, and   wherein the additive element M is at least one element selected from the group consisting of Al, Ni, Cu, Zn, Ga, Ag, In, Sn, Bi, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W.   
     
     
         5 . The R-T-M-B based sintered magnet of  claim 4 , wherein the magnet includes at least one of Tb and Dy as the rare-earth element R. 
     
     
         6 . The R-T-M-B based sintered magnet of  claim 4 , wherein the magnet includes 20 at % or less of Co as the transition metal T.