Synthesis and crystal structure of zirconium tungstate ZrW2O7(OH,Cl)2·2H2 O

Abstract

ZrW ₂ O ₇ (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 ¹⁸⁸ Re medical radioisotope. The structure of ZrW ₂ O ₇ (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) Å, Z=8 and D _c =3.74 g cm ^-3 . Rietveld refinement has been carried out from X-ray diffraction data using Co-Kα radiation over the angular range 15–105° (2θ) and converged with R _wp =8.85%, R _p =6.60%. The structure consists of regular ZrO ₇ pentagonal bipyramids and distorted WO ₆ octahedra, connected in a three-dimensional framework. The terminal hydroxy groups of tungsten polyhedra are statistically substituted by Cl.