VIBRATIONAL AND XRD STUDY OF THE SYSTEM CDWO4-CDMOO4

Mixed oxide powders belonging to the system CdMoxW1-xO4 have been prep ared by a hydrothermal method. They have been characterized by the Rie tveld analysis of their XRD patterns and by IR and Raman skeletal spec troscopies. Virtually pure wolframite-type structures have been obtain ed for x less than or equal to 0.25 and virtually pure scheelite-type structures have been obtained for x greater than or equal to 0.75. The vibrational spectra of both phases have been interpreted on the basis of the correlation method. In both solid solutions the Raman peaks du e to the stretching modes of ''terminal'' W,Mo-O bonds split, while th e corresponding IR bands shift significantly. The effect of the nature of tungsten coordination on the vibrational spectra is briefly discus sed in relation to the use of vibrational spectroscopies to determine the structure of the surface species in supported tungsten oxide catal ysts.