R-T-B based sintered magnet and motor

1. An R-T-B based sintered magnet comprising R 2 T 14 B crystal grains and two-grain boundary parts between the R 2 T 14 B crystal grains,

wherein the two-grain boundary parts are formed at least by:

(i) a phase containing R, Cu, Co, Ga and Fe with an atomic ratio of 40≤R≤70, 1≤Co≤10, 5≤Cu≤50, 1≤Ga≤15, and 1≤Fe≤40 exist, R+Cu+Co+Ga+Fe=100, R is at least one selected from rare earth elements, T is Fe and optionally one or more other elements of iron group, and

(ii) a phase containing R, Cu, Ga, Fe and optionally Co with an atomic ratio of 10≤R≤20, 0≤Co<0.5, 0<Cu<1, and 1≤Ga≤10 exist, R+Cu+Co+Ga+Fe=100, and

the contents of the elements relative to the total mass in the R-T-B based sintered magnet are shown as follows:

R: 29.5 to 33.1 mass %;

B: 0.75 to 0.95 mass %;

Ga: 0.01 to 1.0 mass %;

Cu: 0.01 to 1.5 mass %;

Co: 0.3 to 3.0 mass %;

Al: 0.03 to 0.6 mass %;

Fe: balance, substantially;

the total content of elements other than Fe occupying the balance: 5 mass % or lower,

the ratio of Nd and Pr in R is 95 to 100 atomic %, and

the content of heavy rare earth elements in total mass of the R-T-B based sintered magnet is 1.0 mass % or less.

2. The R-T-B based sintered magnet according to claim 1 , wherein the average thickness of the two-grain boundary parts formed by said phase is 5˜500 nm.

3. A motor comprising the R-T-B based sintered magnet according to claim 1 .

4. A motor comprising the R-T-B based sintered magnet according to claim 2 .