Fourier transform Raman spectroscopic study of Ba(SO4)x(CrO 4)1x solid solution

Abstract

Ba(SO4)x(CrO4 )1−x solid solution (nature: hashemite) gel-grown crystals were studied using Fourier transform Raman spectroscopy. The complex Raman spectrum of the end-member BaCrO4 was studied in detail by means of bandshape analysis and component fitting procedures. Important effects of the crystalline field (both static and dynamic) were observed that could explain the evolution of the chromate anion Raman-active internal modes under the influence of a second anion. Significant modifications were likewise detected in the sulphate anion normal modes. The hindrance of the sulphate intermolecular couplings (dynamic effect of the crystalline field) when chromate anion replaces it in the unit cell could be the cause of the reported observations. It was possible to propose a qualitative assignment of the observed barium chromate Raman-active lattice modes by studying the evolution of such bands with the anion content. The six bands observed in the region 80–200 cm−1 of the barium chromate Raman spectrum can be interpreted as anion libration (one band), chromate anion translational vibrations (two bands) and barium–oxygen vibrations (three bands). Copyright © 1999 John Wiley & Sons, Ltd.