A value of 67.5 kOe has been measured for the room temperature coercivity of an isotropic, heat treated, 1-5 samarium-cobalt plasma sprayed deposit. This value is believed to be the largest published, so far, for a permanent magnet. Sprayed magnets are generally found to be better than 93 percent dense with coercivities of 35 to 60 kOe. Deposits comprised of fine microstructures yield broad, unresolved x-ray diffraction peaks. Low temperature crystallization of these deposits yields diffraction patterns representative of the high temperature equilibrium structure. The emergence of peaks, ascribed to SmCo5, from a low temperature 700 °C heat treatment implies both formation and stability of the SmCo5 phase at this temperature. These results dispute the existence of the generally accepted eutectoid decomposition reaction for SmCo5 at 750–800 °C. If such a reaction were present the products of crystallization should have included Sm2Co7 and not SmCo5. High temperature investigations on sprayed magnets indicate that temperatures of 1100 °C result in low values of coercivity, possibly due to grain growth.

No abstract

No abstract