Abstract:Nd-F species in NdF₃-LiF melts were studied using cryoscopic method. Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA). Based on the different model calculations, NdF₄⁻ was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF₃ was lower than 20%, considering only one single Nd species in the melt, and which was formed in accordance with Temkin model or Flood model. Then, activities of different components in the melts were researched. The results show that activity of LiF decreases, and that of NdF₃ increases with increasing the mole fraction of NdF₃. The value of activity coefficient of NdF₃ is higher than 1, and that of LiF is lower than 1.

Key words: structural entities; NdF₃-LiF melts; cryoscopic method; liquidus temperature