Hydrothermal single crystal growth of calcite in ammonium acetate solution

Abstract

Calcite single crystals were successfully grown in newly discovered ammonium acetate solution, an organic salt solution, under mild hydrothermal conditions below 250°C at saturated vapor pressure. The growth rate increased with the increase in growth temperature, temperature difference, and concentration of ammonium acetate solution. Even in a dilute ammonium acetate solution of 0.07M with a pH of 7.0, the seed crystal grew at a growth rate of 57 μm/day at 235°C with a temperature difference of 15°C. The grown crystal under these conditions was optically transparent and not contaminated with the mineralizer. Ammonium acetate solution has a large difference as a mineralizer for crystal growth of calcite from other inorganic salt solutions; In ammonium acetate solution, new planes, the f and a planes, developed on the seed crystal bound by the r planes.