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The Ikaite to Vaterite Transformation: New Evidence from Diffraction and Imaging

DOI: 10.1107/S0021889809005810 DOI Help

Authors: F. Azough (University of Manchester) , K. Kato (SPring-8) , A. R. Lennie (Diamond Light Source) , J. E. Parker (Diamond Light Source) , C. C. Tang (Diamond Light Source) , S. P. Thompson (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Applied Crystallography , VOL 42 , PAGES 225-233

State: Published (Approved)
Published: April 2009

Abstract: Vaterite is one of three polymorphs of calcium carbonate (CaCO3) found in nature, the others being calcite and aragonite. Here the formation of vaterite from decomposition of ikaite (CaCO3·6H2O) was investigated using synchrotron powder diffraction and scanning electron microscopy. The crystallite sizes of vaterite (40 nm) were found to be much smaller than those of the precursor ikaite (0.5-1.0 µm) as a result of vaterite nucleating as ikaite dehydrates. The rate of decomposition to vaterite increases with temperature, indicating kinetic control of this transformation. It is postulated that the structural arrangement of the hydration sphere around Ca2+ in ikaite determines the orientation of Ca2+ and CO32- ions such that vaterite nucleates upon dehydration. This implies that the dehydration of a precursor hydrated phase such as ikaite is required for vaterite nucleation.

Journal Keywords: Vaterite; Ikaite; Calcium Carbonate

Subject Areas: Environment, Materials, Chemistry

Instruments: NONE-No attached Diamond beamline