Oxidative processes during heat treatment in intermetallic SmCo5 powder

Abstract

Understanding of the thermal stability of intermetallic SmCo5 powder is essential for designing the working atmosphere in all phases of the technological procedure in the production of sintered SmCo5 magnets to obtain maximal magnetic properties. The thermal stability of the SmCo5 powder with defined chemical composition and particle size was investigated in the interval from 20 to 900*C. It was found by thermogravimetic analysis (TGA) that up to 240*C, the oxidation of SmCo5 does not occur. X-Ray diffraction of the thermogravimetric experimental residue of the SmCo5 powder, heated at 240*C, yielded only the presence of the SmCo5 phase. By X-ray diffraction analysis different crystal forms were identified depending on the maximal heating temperature. The following phases were identified: Sm2O3, Co, CoO, Co3O4 and SmCoO3. According to TG and X-ray results, for each of the investigated temperatures, the corresponding chemical reactions were established. The experimental data from both the thermal and X-ray investigations confirm that the phases of pressing and aligning the SmCo5 powder, in the process of producing sintered SmCo5 magnets, may be performed without a protective atmosphere.