Abstract
Two series of hydrated fluorides have been prepared by a “chimie
douce” process. For the first family, more than twenty five compounds
of δ-ALn3F10,xH2O (A+ = alkaline
ions, NH4+, H3O+ and Ln = lanthanide)
have been prepared. They crystallize in the Fdm
space group (a ≈ 15.4 Å and Z = 16)
and are isotypic with δ-(H3O)Yb3F10,xH2O
(x = 1). The diamond-type structure of these phases
(diamond stacking of octahedral units of antiprisms, called UOA[8]),
creates cavities and tunnels where the water molecules can move.
The
second family, γ-ThLn2F10,H2O (Ln3+ = Er3+,
Dy3+ and Yb3+) results from the substitution of Ln3+
and A+ by a tetravalent cation. The new compound γ-ThEr2F10,H2O
(Fmm space group, a = 10.739(1) Å
and Z = 8) is isotypic with γ-KYb3F10.
Water molecules are located inside the tunnels (8c sites) of a CCP stacking
of UOA[8] through which they can move.
For both series, the thermal stability and the zeolitic behaviour, studied by DTA/TGA and X-ray thermodiffractometry, are reported and a low zeolitic water capacity, around 2–4% in mass, is observed.