The Lanthanides, Rare Earth Elements

Abstract

The lanthanides, known also as lanthanoids or rare earth elements (REEs), consist of 17 elements with remarkable properties that have made them emerge in the twenty‐first century as a highly‐valued commodity by the world's industrialized nations. REEs form the largest chemically coherent group in the periodic table. China has led the world production of REEs for decades. The diverse applications of REEs for national defense, energy production and storage, high‐strength magnets, lasers, and medical diagnostics and therapeutics, combined with China's restrictions on supply beginning in 2010, have led to a near‐crisis consisting of national stockpiling, frantic exploration for new deposits, and intense efforts to conserve, recycle and substitute for REEs. The unique physical, chemical and magnetic properties of REEs become particularly interesting at the nanoparticle size, leading to an explosion of research in the last two decades. For these reasons, the commercial and academic pressure to explore new applications of REEs risks outpacing essential research on the toxicology of REEs.