Vibrational and XRD Study of the System CdWO₄−CdMoO₄

Abstract

Mixed oxide powders belonging to the system CdMo x W 1 - x O 4 have been prepared by a hydrothermal method. They have been characterized by the Rietveld analysis of their XRD patterns and by IR and Raman skeletal spectroscopies. Virtually pure wolframite-type structures have been obtained for x ≤ 0.25 and virtually pure scheelite-type structures have been obtained for x ≥ 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 due to the stretching modes of “terminal” W,Mo−O bonds split, while the corresponding IR bands shift significantly. The effect of the nature of tungsten coordination on the vibrational spectra is briefly discussed in relation to the use of vibrational spectroscopies to determine the structure of the surface species in supported tungsten oxide catalysts.