Anisotropic rare earth sintered magnet and method for producing same
An anisotropic rare earth sintered magnet represented by the formula (R 1-a Zr a ) x (Fe 1-b CO b ) 100-x-y (M 1 1-c M 2 c ) y . R is Sm and at least one element selected from rare earth elements, M 1 is at least one element selected from the group consisting of V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si, M 2 is at least one element selected from the group consisting of Ti, Nb, Mo, Hf, Ta, and W, and x, y, a, b, and c each satisfy 7≤x≤15 at %, 4≤y≤20 at %, 0≤a≤0.2, 0≤b≤0.5, and 0≤c≤0.9. The magnet includes 80% by volume or more of a main phase composed of a compound of a ThMn 12 type crystal, the main phase having an average crystal grain size of 1 μm or more, and an intergranular grain boundary phase being formed between adjacent main phase grains.
1 . An anisotropic rare earth sintered magnet represented by the formula (R 1-a Zr a ) x (Fe 1-b Co b ) 100-x-y (M 1 1-c M 2 c ) y (wherein R is a combination of Sm and one or more elements selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; M 1 is at least one element selected from the group consisting of V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si; M 2 is at least one element selected from the group consisting of Ti, Nb, Mo, Hf, Ta, and W; x, y, a, b, and c each satisfy 7≤x≤15 at %, 4≤y≤20 at %, 0≤a≤0.2, 0≤b≤0.5, and 0≤c≤0.9), the magnet comprising 80% by volume or more of a main phase composed of a compound of a ThMn 12 type crystal and containing an R-rich phase and an R(Fe,Co) 2 phase in a grain boundary portion, the main phase having an average crystal grain size of 1 μm or more, an intergranular grain boundary phase being formed between adjacent main phase grains and a Sm/R ratio in an inner portion of the main phase grain being lower than Sm/R ratios of the R-rich phase and the R(Fe,Co) 2 phase.
2 . The anisotropic rare earth sintered magnet according to claim 1 , wherein the intergranular grain boundary phase contains R in an amount of 20 at % or more.
3 . The anisotropic rare earth sintered magnet according to claim 1 , wherein the intergranular grain boundary phase has a thickness of 0.5 nm or more.
4 . The anisotropic rare earth sintered magnet according to claim 1 , wherein the R-rich phase and an R(Fe,Co) 2 phase are contained in an amount of 1% by volume or more in total.
5 . The anisotropic rare earth sintered magnet according to claim 1 , wherein a Sm/R ratio in an inner portion of the main phase grain is lower than a Sm/R ratio in an outer shell portion of the main phase grain.
6 . The anisotropic rare earth sintered magnet according to claim 1 , wherein Sm is not contained in an inner portion of the main phase grain.
7 . The anisotropic rare earth sintered magnet according to claim 1 , wherein the magnet exhibits a coercive force of 5 kOe or more at room temperature, and a temperature coefficient β of the coercive force is −0.5%/K or more.