Phase equilibria in the YbCl2-MCl (M = Li, Na, K) binary systems

Differential scanning calorimetry technique was used to investigate phase equilibria in the YbCl2-MCl (M = Li, Na) binary systems. The YbCl2-LiCl system exhibits an eutectic located at YbCl2 mole fraction x = 0.415 (733 K) and a LiYb2Cl5 stoichiometric compound that is formed at 711 K and melts incongruently at 742 K. The YbCl2-NaCl system exhibits an eutectic located at YbCl2 mole fraction x = 0.559 (764 K). In both systems the formation of solid solutions in the MCl-rich side (M = Li, Na) has been found. The molar enthalpies of mixing (Delta H-MIX) in the liquid YbCl2-MCl (M = Na, K) mixtures have been measured at 1085 K with a Calvet-type high temperature microcalorimeter in the entire range of composition. A negative value of mixing enthalpy was observed for all melts. The minimum value was of approximately: - 2.5, and - 7.5 kJ mol(-1), for systems with NaCl and KCl, respectively. All the experimental results along with the available literature data were used to optimize the thermodynamic properties of the investigated systems using the CALPHAD method.

Automated summary

The phase equilibria in the YbCl2-MCl (M = Li, Na) binary systems were investigated using differential scanning calorimetry technique. The YbCl2-LiCl system exhibited a eutectic and a stoichiometric compound LiYb2Cl5. The YbCl2-NaCl system exhibited a eutectic as well. Solid solutions were found in both systems. The mixing enthalpies of liquid YbCl2-MCl (M = Na, K) mixtures were measured and found to be negative values.