Synthesis of Mesoscopic Particles of Multi-Component Rare Earth Permanent Magnet Compounds

Abstract

Multielement rare earth (R)-transition metal (T) intermetallics are arguably the next generation of highperformance permanent magnetic materials for future applications in energy-saving and renewable energy technologies. Pseudobinary Sm 2 Fe 17 N 3 and (R,Zr)(Fe,Co,Ti) 12 (R = Nd, Sm) compounds have the highest potential to meet current demands for rare-earth-element-lean permanent magnets (PMs) with ultra-large energy product and operating temperatures up to 200°C. However, the synthesis of these materials, especially in the mesoscopic scale for maximizing the maximum energy product ((BH) max ), remains a great challenge. Nonequilibrium processes are apparently used to overcome the phase-stabilization challenge in preparing the R-T intermetallics but have limited control of the material's microstructure. More radical bottom-up nanoparticle approaches based on chemical synthesis have also been explored, owing to their potential to achieve the desired composition, structure, size, and shape. While a great achievement has been made for the Sm 2 Fe 17 N 3 , progress in the synthesis of (R,Zr)(Fe,Co,Ti) 12 magnetic mesoscopic particles (MMPs) and R-T/T exchange-coupled nanocomposites (NCMs) with substantial coercivity (H c ) and remanence (M r ), respectively, remains marginal.