Magnetic Properties of Sintered (PrLa)Co5 Type Magnets

摘要

Since PrCo5 has high intrinsic permanent magnet properties, namely, saturationmagnetization of 12.4 kG at room temperature, anisotropy field of 145 kOe and Curie temperature of 632 C, It offers a great potential for high energy permanent magnet fabrication. However, chemical instabilities and the precipitation of impurity phases etc. have made it difficult to fabricate high energy magnets. In practice, no magnet with energy product (BH) (max) greater than 30 MGOe has been obtained yet. The theoretically expected maximum energy product is about 39 MGOe. This difference is attributed to impurity phases, such as Pr2Co17 and Pr5Co19, present in the magnet, the former being planar and the latter exhibiting a weak anisotropy (38 kOe). Therefore these impurity phases severely degrade coercivity. The highest energy product, 26 MGOe, with coercivity of 4 to 5 kOe was reported by Wallace et al., using high purity Pr from the Ames Laboratory. Substitution of Sm for Pr has been found to increase coercivity effectively. Since SmCo5 has a higher anisotropy field (210 kOe), with a 25% substitution of Sm for Pr provided magnets with coercivity greater than 10 kOe and energy product of 25 MGOe.