High-temperature oxidation resistance and magnetic properties of Si-doped Sm ₂Co ₁₇-type magnets at 500 °c

The high-temperature oxidation resistance and magnetic properties of Si-doped Sm ₂Co ₁₇-type magnets at 500 °C were systematically investigated. The Sm(Co _0.76, Fe _0.1, Cu _0.1, Zr _0.04) ₇Si _x (x=00.6) magnets were prepared by the conventional powder metallurgical technique. It is found that the addition of silicon in the Sm ₂Co ₁₇-type magnet can remarkably improve its oxidation resistance. Moreover, a small amount of silicon addition can also increase its high-temperature intrinsic coercivity. A maximum intrinsic coercivity of 6.7 kOe at 500 °C was obtained for the Sm ₂Co ₁₇-type magnet with Si content x=0.4, whose high-temperature maximum energy product loss was about 2.5 times smaller than pure Sm ₂Co ₁₇-type magnet after oxidation at 500 °C for 100 h, indicating the enhanced oxidation resistance. Its corresponding Curie temperature and saturation magnetization are about 723.9 °C and 7.4 kG, respectively.