Raman Spectroscopic Investigations of ZrSiO4:V4+, the Blue Zircon Vanadium Pigment

Abstract

Powdered and single-crystal samples of the vanadium-containing zircon pigment ZrSiO4:V4+ were investigated by means of Raman spectroscopy, the spectra being recorded between 200 and 1100 cm−1 at ambient conditions. V–O vibrational bands could be identified by comparison with spectra of pure ZrSiO4. The possibility of V4+ occupation of the interstitial 8d site withC2hsymmetry was excluded on group theoretical grounds. V—O bond lengths for ZrSiO4:V4+ were estimated to be between 172 and 175 pm from the Raman band wavenumbers; these bond lengths are much shorter than those (204 and 227.6 pm) expected for V4+ on the Zr4+ site, but similar to that for V4+ on the Si4+ site (175.8 pm). This would indicate substitution on the Si4+ site, 4b, rather than the Zr4+ site, 4a. This conclusion is supported by the influence of V4+ and dopants such as Cr4+, Pr4+ and others on the zircon crystal lattice. The changes in the strengths of Si—O bonds with the change of chromophore incorporated into the structure are reflected in the shifts in wavenumber of the Raman-active zircon modes.