Reinvestigation of phase equilibria in TbCl3–LiCl binary system

Abstract

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.