Bulk structural properties of single phase crystalline (MO0.91V0.09)(5)O-14 and (MO0.68V0.23W0.09)(5)O-14 materials were investigated using in situ X-ray diffraction and in situ X-ray absorption spectroscopy at three metal edges. Temperature programmed experiments in reducing (propene) and oxidizing (oxygen) atmosphere and isothermal redox experiments at 773 K revealed differences in the bulk properties of the two phases studied. A structure stabilizing effect of tungsten in (MOVW)(5)O-14 under oxidizing conditions was found. Moreover, tungsten centers in a (MoVW) dioxide material exert a structure-directing effect towards re-oxidation to a Mo5O14-type structure. (c) 2007 Elsevier B.V. All rights reserved.