Structure and Magnetic Properties of Heat-Resistant Sm(Co_{0.796-<i>x</i>}Fe_0.177Cu<i>_x</i>Zr_0.027)_6.63 Permanent Magnets with High Coercivity

The structure and temperature stability of high-temperature permanent magnets Sm(Co_0.796−xFe_0.177Cu_xZr_0.027)_6.63 (x = 0.117 and 0.130) were studied using x-ray diffraction analysis, thermomagnetic analysis, and scanning and transmission electron microscopy. The magnets have a nanocrystalline cellular structure composed of the R2:17 cell phase, 1:5 boundary phase (27–28% by volume), and Z-phase platelets. The 1:5 phase is formed in the course of isothermal annealing at 850°C and exists in the entire temperature range from 850°C to 400°C. The Curie temperature of the R2:17 and 1:5 phases is approximately 815°C and 580°C, respectively. The magnets have the following hysteresis properties at room temperature: B_r = 890–920 mT, _JH_c = 2.4–2.6 MA/m, _BH_c = 629–676 kA/m, and (BH)_m = 143–159 kJ/m³. In the temperature range of 20–500°C, the temperature coefficients of B_r and _JH_c of the magnets (x = 0.117 and 0.130) do not exceed |− 0.070| and |− 0.172|%/°C, respectively.