Phase diagram of NdI3-RbI pseudo-binary system. Thermodynamic properties of solid compounds

摘要

Phase equilibria in the NdI3-RbI binary system were established from differential scanning calorimetry (DSC) measurements. This system exhibits three compounds, namely Rb3NdI6, Rb2NdI5 and RbNd2I7, and two eutectics located at NdI3 molar fractions x=0.177 (T=810 K) and x=0.421 (T=706 K), respectively. Rb3NdI6 undergoes a solid-solid phase transition at 718K and melts congruently at 905K. Rb2NdI5 and RbNd2I7 melt incongruently at 711K and 737K, respectively. The heat capacity of solid and liquid Rb3NdI6 has been measured in temperature range 298-1006 K. The all of accessible data were used for optimization of phase diagram by the CALPHAD method. Liquid model of associated solution with one associate has been used for description of the liquid phase. The dependence of mixing entropy on composition were determined and interpreted. For the pseudo-binary compounds, existing in investigated system, dependence of Gibbs energies of formation on temperature were calculated. (C) 2015 Elsevier B.V. All rights reserved.