Phase equilibria of the TbCl3–LnCl3 systems: a comparative thermodynamic study

Abstract The phase equilibria investigations of the TbCl 3 –LnCl 3 (Ln = La, Nd) systems, emphasizing the thermodynamic properties and phase diagrams have been presented. The growing demand for rare earth elements, necessitates efficient extraction and separation processes, often involving molten salt systems. While the thermal properties of individual lanthanide halides are quiet well studied, data on their binary mixtures, especially those with different crystallographic structures, are limited. This work focuses on the TbCl 3 –LaCl 3 system, using differential scanning calorimetry (DSC) and differential thermal analysis (DTA) to investigate phase transitions and construct phase diagram. The CALPHAD method was employed for thermodynamic modeling, incorporating both experimental and literature data on TbCl 3 –NdCl 3 system. The results reveal that both systems exhibit eutectic behavior with partial miscibility in the solid phase, providing essential insights for optimizing processes involving these lanthanide halides.