Doping Incompatible Elements into Calcite through Amorphous Calcium Carbonate

Doping large amounts of a incompatible element into calcite, a polymorph of CaCO3, was achieved by pressurizing amorphous calcium carbonate (ACC) containing a dopant. Strontium-doped ACC samples were prepared from supersaturated solutions. ACC was transformed to calcite at 0.8 GPa and 25 degrees C. The lattice volume of calcite obtained by pressurizing ACC increased monotonically up to 372.5 angstrom 3 (1.3% increase from a Sr-free sample) with increasing Sr content in ACC up to 0.15 in Sr/(Sr + Ca). For comparison, the lattice volumes of calcite samples precipitated from supersaturated CaCO3 solution containing Sr were obtained, but the lattice volume of calcite precipitated from supersaturated solutions showed no noteworthy increase. Results of this study indicate that pressure-induced crystallization is an efficient pathway to dope incompatible elements into crystals.