The structure of D_0.53WO₃ has been determined by a room temperature powder neutron diffraction study. The unit cell is body centered cubic (Im³) and contains 8 formula weights (a = 7.562 ± 0.002 Å). The average cell content was refined by a least squares method based on peak intensities. The tungsten atoms lie on the special sites of the perovskite structure and are surrounded by nearly regular octahedrons of oxygen atoms with the latter displaced from the normal perovskite positions along 〈110〉. The deuterium atoms constitute statistically distributed -OD bonds which are directed towards the nearest oxygen atom of a neighboring octahedron. The analogous hydrogen compound(cubic hydrogen tungsten bronze) is best described as a nonstoichiometric oxide hydroxide WO₃−x(OH)_x based on a distorted ReO₃ structure. The crystal structure is closely related to that of In(OH)₃ and Sc(OH)₃.

 

In order to understand the slow stages of the catalytic reduction of WO3 to hydrogen tungsten bronzes H_xWO₃, the mobility of hydrogen in the latter has been studied by NMR spectroscopy between −50 and −195 °C. Values of the spin-lattice relaxation time T1 plotted vs. the inverse temperature show a minimum indicating one main relaxation process, namely that due to diffusion. The corresponding calculated diffusion coefficient of H in H_xWO₃ is very high. Thus transport of H in H_xWO₃ cannot be the rate determining step in the catalytic reduction of WO₃ Rather, that step is suggested to be the penetration of the reducing species below the surface of WO₃ into the lattice.