Photoemission studies of polymorphic CaCO3 materials

The surface analysis of polymorphic calcium carbonate (CaCO3) compounds, namely, calcite, aragonite, and vaterite were carried out by X-ray photoelectron spectroscopy (XPS). XPS results clearly demonstrate that vaterite is different from the other two and exhibit a low binding energy (BE) for all its constituent elements. It is attributed to the perpendicular orientation of CO32− to ab plane in vaterite. Aragonite shows less calcium and more oxygen and indicates the surface is carbonate terminated. Intergrowth of calcite and aragonite and natural dolomite samples were also analysed and compared with the above CaCO3 compounds. Ca:Mg=3 suggest that the dolomite surface is dominated by Ca.