R.W. Smaha, S. O’Donnell, R. Kuchi, Y. Wu, R. Kinner, S.R. Bauers, F. Johnson, I. Hlova, M.J. Kramer
National Renewable Energy Laboratory,
United States
Keywords: permanent magnets, critical materials
Summary:
Current high-performance permanent magnets contain critical rare-earth materials such as Nd and Dy, so alternative materials with less or no critical elements are highly desired. To address this, we see an opportunity in nitride magnets. Several nitride-based compounds show great promise as permanent magnets containing little or no rare-earth elements. For example, α''-Fe16N2 exhibits a magnetization in excess of the Slater-Pauling limit, and Sm2Fe17N3 is promising for high-temperature applications. Fe is the 4th most abundant crustal element and N is the most abundant atmospheric element. In particular, nanoparticles of these nitride materials exhibit high magnetization and a promising magnetocrystalline anisotropy. However, achieving adequate magnetic properties can be a challenge for new materials, particularly nitrides, which often have low thermal stability. Commercial magnets must be dense, which is achieved for current materials using a high-temperature sintering process that degrades nitride magnets. Developing innovations in processing and manufacturing is therefore key to future commercialization of this promising technology. We will discuss recent developments in synthesizing and processing these materials, focusing on the challenges in forming dense, grain-aligned magnets. Overcoming these challenges will permit widespread adoption of critical-material-lean permanent magnets and therefore mitigate uncertainties in the supply chain and cost of permanent magnets.