Structural characterization of new Tl+ and Pb2+ oxyfluoridozirconates deriving from hexagonal layer structures of M’xM3×9–13 general formula

A new series of Tl + and Pb 2+ oxyfluoridozirconates is isolated and structurally described in hexagonal symmetry, P6 3 /mmc space group and close lattice parameters ( a = 7.649 Å and c = 15.797 Å for Tl 0.69 Zr 3 O 1.91 F 8.87 ; a = 7.647(2) Å and c = 15.835(4) Å for Pb 0.714 Zr 3 O 2.90 F 7.62 ). The refined Tl content varies from 0.69/1 to 0.90/1 (0.71 to 0.76 for Pb) and is never stoichiometric. Their structure corresponds to a stacking of hexagonal layers containing a strong framework of ZrOF 7 bicapped trigonal prisms and ZrO 2 F 5 pentagonal bipyramids sharing edges and vertices and forming triangular clusters of formula comprised between Zr 3 OF 18 and Zr 3 O 4 F 12 . These units are all centered on one O anion and interconnected via F corners with three other triangular units forming layers delimiting holes of distorted hexagonal section partly occupied by Tl + or Pb 2+ cations. This new type is compared to many structures presenting various stackings of similar hexagonal or pseudo-hexagonal layers with M 3+ or M 4+ cations of high size coordinated by 6, 7, 7 + 8, 8, 8 + 9, 9 F and/or O anions. All belong to a same family of phases of M’ x M 3 X 9–13 general formula.