The clathrate Ba8CuxGe46-x-y□y: Phase equilibria and crystal structure

Phase relations at 700 deg. C, 800 deg. C and solidus temperatures have been derived for the clathrate system Ba8CuxGe46-x-y□y via X-ray single crystal and powder diffractometry combined with electron probe micro analysis and differential thermal analysis. The ternary clathrate phase derives from binary Ba8Ge43□3 and extends up to x=6. Structure investigations define cubic primitive symmetry with the space group type Pm3-barn consistent with a clathrate type I structure throughout the entire homogeneity region 0<x≤6 but defect-free Ba8CuxGe46-x exists for x≥5.5. - Graphical Abstract: Cages and atom thermal displacement parameters in clathrate Ba8CuxGe46-x-y□y for Ba8Cu2Ge42□2 and Ba8Cu6Ge40.