Thermodynamic Re-assessment of the Lanthanum-Tin System

The lanthanum-tin system has been critically re-assessed based on available experimental data by the CALPHAD (CALculation of PHAse Diagram) method. The liquid phase was characterized by both the associated solution and substitutional solution models, while the seven intermetallics were treated as stoichiometric compounds. La1Sn1 was chosen as the associated complex in the associated solution model. The Redlich–Kister polynomial was used to describe the excess Gibbs energy of the substitutional solution model. Two sets of self-consistent thermodynamic parameters for the La-Sn system were finally obtained. The calculated results based on the thermodynamic parameters agree well with the phase diagram data and the thermodynamic data. Calculations using both sets of thermodynamic parameters obtained in the present work reproduce the experimental data reasonably well. Compared with previous assessments utilizing the associated solution and substitutional solution models, significant improvements have been made in the present work.