[Zn3+xV2-xO7-3x(OH)2+3x]•2H2O and M[Zn3-xV2O7(OH)2]Cl1-2x•(1+2x)H2O two families of zinc vanadates with structures related to the hexagonal structure of [Zn3V2O7(OH)2]•2H2O

[Zn3+xV2-xO7-3x(OH)(2+3x)](.)2H(2)O (I), with 0 < x < 0.66 and M[Zn3-xV2O7(OH)(2)]Cl-1-2x(.)(1 + 2x)H2O (II), with 0.15 < x < 0.5. were obtained by hydrothermal synthesis at 170 degreesC (24 h) from gels with the molar composition ZnCl2; aV(2)O(5); bMOH; 228H(2)O, with M = Li, Na, NH4 or K for (I) and NH4 or Rb for (II); 0.2 < a < 0.5 and 0.5 < b < 6. The compounds of both families crystallize in the hexagonal system with a structure which can be related to the structure of [Zn3V2O7(OH)(2)](.)2H(2)O. Their Zn/V molar ratio can be determined from to the unit-cell parameter a(0) by the linear relations Zn/V = 4.896a(0) - 28.124 (R = 0,988) for (I) and Zn/V = 15.302a(0) - 91.027 (with R-2 = 0.992) for (II). In (I) the negative charges created by the substitution of vanadium with zinc in the tetrahedra of the pyrovanadate pillars connecting the octahedral sheets containing the zinc, are compensated by protonation of framework oxygen atoms. In (II) the negative charges, created by the removal of zinc in the octahedral sheet, are compensated by cations (NH4+ or Rb+) located between the pyrovanadate pillars. But in order to fill more completely the space, additional cations (NH4+ or Rb+) are incorporated in form of the chloride salt. (C) 2004 Elsevier SAS. All rights reserved.