High-Coercivity Anisotropic SmFeN Magnetic Materials

摘要

We prepared Ti-added Sm_2Fe_(17)N_3 fine powder of approximately 2 μm particle size, which exhibited a high intrinsic coercivity (H_(cj)) of up to 2.0 MA/m, using additive TiO_2 nanoparticles as the grain refinement agent for Sm_2Fe_(17)N_3 powder. By TEM-EDX measurement, XRD analysis and the analysis of grain growth during the R/D reaction, we proposed the formation mechanism, in which added TiO_2 particles strongly retard Sm_2Fe_(17) grain growth by acting as pinning sites in the initial period of the R/D reaction and Ti atoms subsequently diffuse over all the particles. An injection-molded Sm_2Fe_(17)N_3 bonded magnet (resin: PA12) prepared from the Ti-added Sm_2Fe_(17)N_3 powder exhibited an excellent H_(cj) of 1.52 MA/m, a squareness (H_k) of 0.89 MA/m and a (BH)_(max) of 90 kJ/m~3. The irreversible flux losses of the Ti-added Sm_2Fe_(17)N_3 bonded magnet were -0.8% for P_c=2 and -3% for P_c=0.2 after heating to 423 K for 1,000 hr in air.