Influence of Sintering Temperatures on the Phase Structure and Magnetic Properties of Spark Plasma Sintered SmCo5 Magnets

SmCo5 magnets were prepared by spark plasma sintering (SPS) technique. The phase constitutions, magnetic properties, and microstructures of magnets prepared under different sintering temperatures were investigated systematically. It is observed that the 1:5 phase and 2:7 phase coexist in the magnet, and 2:17 phase appears when the temperature rises to 1050 °C. The best magnetic properties were obtained for the magnets prepared at 1000 °C, with remanence Jr = 0.45 T, intrinsic coercivity Hcj = 985 kA/m, and maximum energy density (BH)max = 37 kJ/m3. It is shown that the SPSed magnet prepared at 1000 °C exhibits excellent thermal stability which is described in terms of temperature coefficient of remanence (α) = −0.15%/°C and temperature coefficient of coercivity (β) = −0.25%/°C in the temperature range of 27–400 °C. The microstructure analysis showed that the high density of the magnet and the uniform distribution of the hard magnetic phase are the main reasons for the excellent magnetic properties.