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

Abstract

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.