Synthesis, stability and zeolitic behavior of delta-ALn(3)F(10),xH(2)O and gamma-ThLn(2)F(10),H2O phases (Ln = lanthanide)

Two series of hydrated fluorides have been prepared by a chimie douce process. For the first family, more than twenty five compounds of delta -ALn(3)F(10),xH(2)O (A(+) = alkaline ions, NH4+, H3O+ and Ln = lanthanide) have been prepared. They crystallize in the Fd (3) over barm space group (a approximate to 15.4 Angstrom and Z = 16) and are isotypic with delta-(H3O)Yb3F10,xH(2)O (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, gamma -ThLn(2)F(10),H2O (Ln(3+) = Er3+, Dy3+ and Yb3+) results from the substitution of Ln(3+) and A(+) by a tetravalent cation. The new compound gamma -ThEr2F10,H2O (Fm (3) over barm space group, a = 10.739(1) Angstrom and Z = 8) is isotypic with gamma -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.