Raman and Infrared Spectroscopic Study of Ce1-xMxVO4-0.5x (M=Pb, Sr, and Ca) and Ce1-xBixVO4 Solid Solutions

Raman and infrared spectroscopic studies of Ce1-xMxVO4-0.5x (M=Pb, Sr, and Ca) and Ce1-xBixVO4 solid solutions have been performed. When aliovalent or isovalent cations with similar/different ionic radii were substituted for Ce in CeVO4 to form the substitutional solid solutions, it was found that the valence and/or ionic radii of the substitutes dominated the solid solubility limit, producing different lattice parameter changes/distinctive spectral features with x in Ce1-xMxVO4-0.5x and Ce1-xBixVO4. Particularly, the substitution of aliovalent cations, which causes a change in oxygen stoichiometry to preserve the charge neutrality, led to the emergence of several broad bands in the Raman spectra of Ce1-xMxVO4-0.5x whereas they were absent in Ce1-xBixVO4. The x-dependence of frequency, linewidth, and intensity of the Raman/infrared modes is presented and discussed in order to draw a spectroscopic distinction between Ce1-xMxVO4-0.5x and Ce1-xBixVO4 solid solutions.