Opportunities for Cerium Valorization in the Rare Earth Supply Chain

Rare earth (<i>RE</i>) elements are co-located in ore deposits and must be treated together during the difficult extraction and separation. Cerium is the majority element in most deposits (&gt; 50 %), and the growing need for Nd, Pr and the heavy lanthanides in permanent magnets and other energy transition technologies results in costly stockpiling of cerium oxide which has low demand. Finding new high-value applications for cerium metal or compounds is therefore a sought-after goal to improve the profitability of rare earth mining and processing.<br/>This contribution will highlight the use of cerium in aluminum alloys and the preparation of Ce-based permanent magnets as two emerging technologies for high-value products that have potential to stabilize the fluctuating rare earth market and also substitute critical materials.<br/>The development of aluminum-cerium alloys over the last decade has produced a range of new alloys with superior strength at high temperatures compared to conventional alloys. Despite their excellent properties and the abundance of cheap cerium oxide from rare earth mining, Al-Ce alloys have remained niche for specialty applications. The reduction of cerium oxide to the Ce metal for use in alloying is a major cost factor for the final alloy product and currently no domestic production of Ce metal exists. Our collaboration has developed an alternative process to directly reduce cerium oxide during aluminum alloying ^[1] which drastically reduces the energy requirements and therefore the cost and market entry barrier for Al-Ce alloys.<br/>Permanent magnets based on the <i>RE</i>Fe₁₂N phase are promising alternatives to the established Nd-Fe-B and Sm-Co materials as they have lower rare earth content, and their superior performance has been demonstrated in powders and thin films. The need for stabilizing additives and their narrow processing window have obstructed the preparation of bulk magnets by conventional methods. Here, we will present the potential of advanced processing methods such as laser powder bed fusion and spark plasma sintering for the consolidation of Ce-Fe-N based permanent magnet powders.<br/>Both technologies, the preparation of Al-Ce alloys by directly reducing cerium oxide and the development of bulk Ce-Fe-N magnets using advanced consolidation methods, lead to high value products of the underutilized rare earth element cerium and would support the nascent rare earth industry as well as provide technologies for the pending green energy transition.<br/>Work performed at LLNL under contract DE-AC52-07NA27344.<br/><br/>[1] A. Amon, E. E. Moore, H. B. Henderson, J. Shittu, M. Kunz, S. Kastamo, N. Huotari, A. Loukus, R. Ott, D. Weiss, S. K. McCall, <i>Mater. Horiz.</i> <b>2024</b>, <i>11</i>, 2382–2387.