Experimental investigation and thermodynamic modelling assessment of the AECl₂-NdCl₃ (AE = Sr, Ba) systems

The thermodynamic and thermo-physical properties of the binary salt systems AECl₂-NdCl₃ (AE = Sr, Ba) have been investigated using an experimental and modelling approach. The binary salt systems both include a single intermediate salt, i.e. Sr₉Nd₅Cl₃₃ and Ba₃Nd₂Cl₁₂, respectively. The structure of these intermediates has been investigated with X-ray diffraction (XRD). Furthermore, these systems exhibit mutual solubility of NdCl₃ in BaCl₂ and SrCl₂. The investigation of these solid solutions has been performed using quenching experiments and subsequent post-characterisation by XRD. Phase diagram equilibria have also been investigated using differential scanning calorimetry (DSC). Using the aforementioned information on phase transitions, intermediate compound formation, and solid solubility, thermodynamic assessment of the systems has been performed using the CALPHAD method. The model for the Gibbs energy of the liquid solution is the quasi-chemical formalism in the quadruplet approximation, while the model for the Gibbs energy of the solid solutions is the two-sublattice polynomial model.