Preparation of high-purity cerium via electromagnetic directional solidification

High-purity cerium (Ce) plays a crucial role in modern production processes. This study proposed a novel method for Ce purification via electromagnetic directional solidification. Initially, the segregation coefficients of iron (Fe), silicon (Si), calcium (Ca), and magnesium (Mg) in Ce were calculated. The results indicated that the segregation coefficients for Fe and Si were less than one, while the segregation coefficients for Ca and Mg were closed to one. This indicated that Fe and Si impurities were effectively removed through directional solidification. Experimental results indicated that during the process, Fe and Si impurities were enriched and removed from the top of the solidified material due to the segregation effect. However, Ca and Mg impurities were removed through volatilization, which was attributable to their significantly higher vapor pressure compared with Ce, Fe, and Si. The Ca content was reduced from 0.023 wt% to <0.001 wt% and the Mg content decreased from 0.05 wt% to < 0.001 wt%. Additionally, the effect of pulling-down rates on Ce purification was investigated at rates of 2 mu m/s, 3 mu m/s, and 5 mu m/s. The results indicated that the removal of Fe and Si was more effective at slower pull-down rate. Therefore, this study demonstrated that electromagnetic directional solidification was an efficient method for achieving high-purity Ce.