Formation of Copper–Neodymium Intermetallic Compounds by Carbothermic Reduction of Neodymium Oxide in the Presence of Copper

Abstract

Carbothermic reduction of neodymium(III) oxide (Nd2O3) was performed by arc melting and in a graphite resistance furnace, using copper as a solvent metal. Successful carbothermic reduction was evident by formation of copper–neodymium intermetallics, where predominant phases were found to be Cu6Nd and Cu5Nd. The reduction reaction is proposed to be caused by thermal decomposition of neodymium oxide carbide (Nd2O2C2) forming a molten mixture of neodymium(III) oxide and neodymium dicarbide (NdC2) upon release of carbon monoxide (CO(g)), where subsequent decomposition of neodymium dicarbide was facilitated by a reduction in activity of formed elemental neodymium species solvated in molten copper. Addition of carbon in excess of neodymium oxide carbide stoichiometry was found to correlate with increased concentration of neodymium in copper, likely caused by an increase in concentration of neodymium dicarbide.