Thermal expansion of synthetic aragonite condensed review of elastic properties

Samples of pure aragonite are synthesized by precipitation from aqueous sol ution and used to determine the heat capacity and temperature dependence of the unit cell parameters in the temperature range 291-700 K. The X-ray dif fraction powder diagram at room temperature is refined in space group Pnma and resulted in the cell parameters a = 5.7444(8) Angstrom, b = 4.9620(4) A ngstrom, c = 7.9700(6) Angstrom, and V = 227.17(3) Angstrom(3). TRXD allows the study of the thermal expansion of the lattice up to the phase transiti on to the stable calcite which occurs at 723 K. anisotropic expansion coeff icients are computed in the temperature ranges 291-700 K and 800-900 K for aragonite and calcite, respectively. From heat capacity measurements and hi gh pressure compressibility data from the literature, some elastic coeffici ents of aragonite and calcite, particularly those of the Gruneisen type, ar e reexamined. (C) 1999 Academic Press.