Physical changes in BaSO4 caused by K+ and Fe3+ ions

Abstract

The effects of coprecipitated K+ and Fe3+ ions on the nature of freshly precipitated BaSO4 were studied. The presence of K+ in the precipitate is seen to have a pronounced effect on crystal habit and increases the specific surface area of the crystals. Micro-Raman measurements show a progressive shift in the [Formula: see text], band for precipitates doped with potassium. This shift is seen to be a linear approach toward the v1 frequency of K2SO4. X-ray diffraction studies indicate no marked changes in cell parameters but do reveal changes in relative intensities in the diffraction patterns of potassium-doped precipitates. In the concentration ranges studied, ferric ions show no marked changes in any of the above properties. The changes are interpreted as being due to the formation of solid solution of potassium with barium sulphate, while iron is adsorbed onto the crystal surfaces. This is seen as a novel use of micro-Raman spectroscopy in the study of doped crystals.