Thermodynamics of lanthanide halides and application to high‐temperature processes

Abstract

The physicochemical properties of lanthanides, and of their derivatives, contribute essential functions to a range of modern‐day materials and processes. Some fundamental thermodynamic and electrochemical features of lanthanide halide melts are presented. They are illustrated by a few selected examples of relevance for applications ranging from pyroreprocessing of spent nuclear fuel to electrochemical molten salt synthesis of materials.

Stability field diagrams for Ln–O–Cl systems

“…TbCl 3 exhibits a phase transition at 790 K with crystal structure changing from orthorhombic PuBr 3 -type to orthorhombic trirutile-type. DyCl 3 transforms from low temperature monoclinic (AlCl 3 -type) to orthorhombic (PuBr 3 type) at 611 K. The subsequent lanthanides (Ho to Lu) have monoclinic AlCl 3 -type structure [12]. The different general trends in the variation of stability of Ln 2 O 3 and LnCl 3 compounds provide a tool for the separation of lanthanides.…”