Structural study of amorphous WO₃ thin films prepared by the ion exchange method

The structure of amorphous tungsten trioxide films was investigated with IR and Raman spectroscopic analyses and an XRD method. The films were prepared by ion exchange from sodium tungstate as a starting material. Films consisted of microclusters of 10–30 Å diameter, in which the networks are formed with WO₆ octahedra sharing their corners and edges. The networks in the as-prepared samples consisted of WO₆ units with low symmetry, in which termination by W=O and W—OH₂ groups was common. As the post-annealed temperature became higher, the symmetry of WO₆ was improved and the edge-sharing octahedra disappeared.