Phase relations of the CaO-SiO2-Nd2O3 system and the implication for rare earths recycling

CaO-SiO2-Nd2O3 slags were equilibrated at 1773 K and 1873 K (1500 C and 1600 C) for 24 hours in Ar, and quenched in water to determine the operative phase relations. The composition and crystallinity of the phases in equilibrium were determined by EPMA-WDS and EBSD, respectively. Based on these analyses, the liquid stability region was accurately determined, and a large part of the isothermal section of the phase diagram was constructed. Data resulting from this work can be used to generate a thermodynamic database for rare-earth oxide-containing systems and to support further investigation on separation of rare earths from metallurgical slags or other residues through high-temperature processing.status: publishe