Calcium carbonate with various structures and morphologies were prepared by double injection of the CaCl2 and NH4HCO3 solutions with molar ratio of 1:1 at 30-80 degrees C. The lamellar vaterite particles, the mixture composed of vaterite, aragonite and calcite, and the aragonite whiskers were formed at 30-40 degrees C, 50-70 degrees C and 80 degrees C, respectively. Thermodynamic calculation showed that the value of [CO32-]/[Ca2+] decreased with the increase of temperature, which may be one of the reasons for the formation of the lamellar vaterite at 30-40 degrees C and the aragonite whiskers at 80 degrees C. (C) 2008 Elsevier B.V. All rights reserved.