Reinvestigation of phase equilibria in TbCl3-LiCl binary system

The phase equilibria in the terbium(III) chloride- lithium chloride pseudobinary system were established by means of differential scanning calorimetry. It was established that the pure terbium(III) chloride undergoes solid-solid phase transition at 790 K and melts at 859 K. The TbCl3-LiCl pseudobinary system is characterized by the existence of two compounds. First one, namely Li3TbCl6, forms at 553 K and melts incongruently at 727 K. Second compound, LiTbCl4, decomposes in the solid state at 609 K. The composition of Li3TbCl6-TbCl3 eutectic corresponding to terbium(III) chloride mole fraction x = 0.521 (T = 665 K) was found from Tammann plot, which predict, through application of the lever rule, the variation of the enthalpy associated with eutectic melting as a function of composition. The obtained results have been compared with the literature data concerning for the TbCl3-LiCl pseudobinary system. The phase diagram of the TbCl3-LiCl pseudobinary system was also optimized by CALPHAD method.