During systematic investigations of the phase relationships in the system CaF2-YbF3, special consideration was given to annealing samples for a long time. In this case four fluorite-related superstucture phases were found: Ca2YbF7 (t), Ca9Yb5F33 (rhα), Ca17Yb10F64 (cβ) and Ca8−σYb5+σF31+σ = Ca7+σYb6−σF32−σ (rhβ). The phases t, rhα and rhβ are members of the homologous series (Ca,Yb)mF2m+5 with m
... [Show full abstract] = 15, 14, 13 and cβ is a combination of the phases with m = 14 and m = 13. In the fluorine-rich region of the system there exists a solid solution with tysonite structure and a related ordered phase with the formula Ca3Yb7F27.