Thermochemistry of Neodymium Silicates and Reassessment of the Nd ₂ O ₃ –CaO–SiO ₂ System

To advance the efficient recycling of rare earth metals via high‐temperature processes, a comprehensive understanding of phase relations and thermodynamic properties in rare earth oxide containing slag is essential. In this work, the enthalpies of formation of neodymium silicates (Nd 2 SiO 5 , Nd 14 Si 9 O 39 , and Nd 2 Si 2 O 7 ) were determined using high‐temperature oxide melt drop solution calorimetry in the molten 2PbO–B 2 O 3 solvent at 973 K. Furthermore, a thermodynamic description of the Nd 2 O 3 –CaO–SiO 2 system was reassessed based on experimental phase equilibria and thermodynamic properties, the optimized phase diagrams of the Nd 2 O 3 –CaO–SiO 2 system are in good agreement with the evaluated data.