Synthesis and crystal structure of zirconium tungstate ZrW2O7(OH,Cl)(2)center dot 2H(2)O

ZrW2O7(OH,Cl)(2) . 2H(2)O has been synthesised by refluxing, followed by hydrothermal crystallisation of amorphous zirconium tungstate gels in 1-8 M HCl. It is known that the amorphous Zr tungstate can be used as a gel-generator for production of the Re-188 medical radioisotope. The structure of ZrW2O7(OH,Cl)(2) . 2H(2)O has been refined by conventional powder diffractometer data. The compound crystallises in the tetragonal space group I4(1)cd (no.110) with a=11.4454(4), c=12.4851(7) Angstrom, Z=8 and D-c=3.74 g cm(-3). Rietveld refinement has been carried out from X-ray diffraction data using Co-Ka radiation over the angular range 15-105 degrees (2 theta) and converged with R-wp=8.85%, R-p=6.60%. The structure consists of regular ZrO7 pentagonal bipyramids and distorted WO, octahedra, connected in a three-dimensional framework. The terminal hydroxy groups of tungsten polyhedra are statistically substituted by Cl.