FT-Raman and powder XRD analysis of the Ba(SO 4) x(CrO 4) 1− x solid solution

• Published in: Talanta (Oxford) Vol. 50; no. 2; pp. 391 - 400
• Main Authors: Alia, J.M., Edwards, H.G.M., Garcia-Navarro, F.J.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 1999; Oxford Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Infrared and raman spectra and scattering; Inorganic compounds; Mixed anions; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other nonmetallic inorganics; Physics; Raman; Salts; Solid solutions; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Solid solutions; Mixed anions; Raman; Water; Fourier transformation; Quantity ratio; Raman scattering; Vibrational modes; XRD; Experimental study; Chromates; Quaternary compounds; Barium sulfates; Crystal structure
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/S0039-9140(99)00127-7

The Ba(SO
4)
x
(CrO
4)
1-x
solid solution has been described in nature, forming the mineral Hashemite. From the geochemical point of view, however, anionic solid solutions have much interest because they are suitable systems to probe order–disorder phenomena. The solid solution analysed in the present study has, moreover, a special incentive in its possible use for the extraction from water, and immobilisation, of the pollutant Cr(VI) ion. The orthorhombic (space group Pnma) unit cell parameters of the solid solution change linearly with the mole fraction of both anions, decreasing with increase in the sulfate anion concentration. The vibrational spectroscopic study is centred on the behaviour of the anionic symmetric stretching band (ν
1,
A
1), whose characteristics are examined in detail. While the chromate anion band retains its wavenumber along the full compositional range, the sulfate anion band is shifted toward lower wavenumbers with decrease in the corresponding mole fraction. The positional disorder induced by the random anionic substitution results in strong increase of the halfwidth in both bands, which becomes greatest in the central member of the series.