Incorporation of organic and inorganic impurities into the lattice of metastable vaterite

Vaterite is the least thermodynamically stable and the least abundant anhydrous crystalline phase of calcium carbonate. It is also the least well understood, as its crystal structure is still a matter of debate. Here we consider a new structural aspect of vaterite not previously described: its ability to sustain high strains via intracrystalline incorporation of aspartic acid and via substitution of Mg or Ba for Ca. We report, for the first time, the formation of substituted Mg- and Ba-vaterite, and their dependence on substituted impurity levels as detected by X-ray diffraction and Raman spectroscopy. Mg was substituted for up to 12% of Ca, and Ba for up to 2.5% of Ca, to form crystals of Mg-vaterite and Ba-vaterite with lattice distortions of up to 0.9% and 0.14%, respectively.