Raman Spectrum of Vanadium-Zirconia Yellow Pigment

ABSTRACT

Monoclinic vanadium-zirconia yellow pigments were prepared by gelling mixtures of zirconium n-propoxide and vanadyl acetylacetone. The nature of interactions between the host ion and the foreign cation in the vanadium-zirconia pigment was investigated in order to contribute to a better understanding of the origin of this pigmenting system using Raman scattering measurements. The Raman spectra of powdered samples of the vanadium-zirconia pigment recorded between 100 and 1400 cm⁻¹ show the peaks at 991, 701, and 403 cm⁻¹ assigned to the asymmetric and symmetric stretching and bending vibrations of the V⁴⁺ = O bonds, respectively. The assignment of these peaks was discussed by comparison with Raman spectra of vanadium oxides and on the basis of V-O bond distances deduced from the Hardcastle and Wachs equation and from the valence state of the vanadium cation calculated by Brown in the valence sum rule. This suggests that the V⁴⁺ cations replace Zr⁴⁺ in sevenfold coordinated site in the monoclinic zirconia structure. The V⁴⁺ cation allowing the d-d electronic transition is related to the origin of the lemon yellow coloration.

KEYWORDS:

• Raman spectroscopy
• vanadium-zirconia
• yellow pigment

ACKNOWLEDGMENTS

O. E. Kasende would like to thank Professors W. Kiefer and D. de Waal for their hospitalities at the University of Würzburg, Germany, and University of Pretoria, South Africa, respectively, where Raman spectra were recorded. He is grateful to DAAD for the research visit scholarship at Würzburg and to the ZIUS2009VOA0701/ZIUS2010VOA0701/ZIUS2011VOA0701 VLIR-UOS Program for financial support for a study visit at the University of Leuven where the last version of this paper was completed.

Notes

Intensities in parentheses are abbreviated as vw, very weak; w, weak; m, medium; s, strong; vs, very strong.