Crystal to Calcite: Fabrication of Pure Calcium Carbonate Polymorph in the Solid State

Selective formation of different polymorphs of calcium carbonate (CaCO3) in the solid state using aromatic organic acids as ligands for Ca2+ coordination has been reported. The formation of pure calcite and vaterite phase in bulk amount can be nicely captured by the choice of suitable solid state routes, employed in the preparation of precursor Ca-carboxylic acid complexes. Calcite can be solely obtained via crystallization of Ca-carboxylic acid complexes in a water methanol binary solvent system followed by thermal agitation at 600 C for 6 h. However, vaterite has been primarily obtained under similar conditions upon heating the crystalline powders of the precursory complexes prepared by the solid state grinding technique. The results obtained suggest that solid state techniques could give an alternative and versatile tool for controlling both the structure and the polymorphism of inorganic materials. The formation of intertwined aragonite rods from using trimesic acid as an organic additive instead of ligand is also noteworthy.