Structure of Biogenic Aragonite (CaCO3)

• Published in: Crystal growth & design Vol. 7; no. 9; pp. 1580 - 1583
• Main Authors: Pokroy, B, Fitch, A. N, Zolotoyabko, E
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Washington,DC American Chemical Society 01.09.2007
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Inorganic compounds; Materials science; Methods of crystal growth; physics of crystal growth; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; Crystalline phase; Fluctuations; Lattice distortion; Phase transformations; Calcium carbonates; XRD; Lattice relaxation; Heat treatments; Aragonite; Crystallites; Unit cell; Anisotropy; Growth mechanism; Orthorhombic lattices; Microstructure; Thermal annealing; Synchrotron radiation; Crystal structure
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg060842v

By using high-resolution X-ray powder diffraction at a dedicated synchrotron beam line, ID-31, of the European Synchrotron Radiation Facility (ESRF, Grenoble, France), we studied structural and microstructural modifications in biogenic aragonite crystals, obtained from mollusk shells, and subjected to heat treatments at elevated temperatures. All investigated shells revealed anisotropic lattice distortions of the orthorhombic unit cell as compared to geological aragonite. Annealing at temperatures above 150−200 °C led to pronounced lattice relaxation which is accompanied by a substantial reduction of crystallite sizes and related growth of microstrain fluctuations. These findings indicate that biogenic aragonite crystals are strained, apparently, as a result of the amorphous/crystalline phase transformation, which proceeds within the supporting network of oriented biomacromolecules at early stages of biomineralization.