Synthesis and study of a well crystallized CaCO3 vaterite showing a new habitus

Synthetic CaCO3 vaterite obtained by classical routes consists of shapeless particles. However, owing to their small size (50 nm), the particles tend to agglomerate strongly, thus resulting in spherical packs of 3 mu m average diameter. Transmission electron microscopy studies of isolated particles are therefore very difficult to achieve without submitting these aggregates to treatments that could affect their structural and textural features. We have synthesized pure vaterite particles which do not exhibit this agglomeration phenomenon but present a clearly defined habitus (size, shape, texture). It is therefore possible to prepare microcrystalline monolithic hexagonal platelets of vaterite in the micrometre range that exhibit very good crystallinity. In addition, we have carried out an IR study of this pure vaterite and an assignment of the different absorption bands is proposed, in comparison with the two other CaCO3 modifications.