Letter abstract


Nature Materials 3, 900 - 902 (2004)
doi:10.1038/nmat1263

Subject Categories: Ceramics | Structural materials | Characterisation and analytical techniques

Anisotropic lattice distortions in biogenic aragonite

Boaz Pokroy1, John P. Quintana2, El'ad N. Caspi3, Alex Berner1 and Emil Zolotoyabko1

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Composite biogenic materials produced by organisms have a complicated design on a nanometre scale1, 2, 3. An outstanding example of organic–inorganic composites is provided by mollusc seashells, whose superior mechanical properties are due to their multi-level crystalline hierarchy4, 5 and the presence of a small amount (0.1–5 wt%)6 of organic molecules2, 7. The presence of organic molecules, among other characteristics, can influence the coherence length for X-ray scattering in biogenic crystals8, 9, 10. Here we show the results of synchrotron high-resolution X-ray powder diffraction measurements in biogenic and non-biogenic (geological) aragonite crystals. On applying the Rietveld refinement procedure to the high-resolution diffraction spectra, we were able to extract the aragonite lattice parameters with an accuracy of 10 p.p.m. As a result, we found anisotropic lattice distortions in biogenic aragonite relative to the geological sample, maximum distortion being 0.1% along the c axis of the orthorhombic unit cell. The organic molecules could be a source of these structural distortions in biogenic crystals. This finding may be important to the general understanding of the biomineralization process and the development of bio-inspired 'smart' materials.

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  1. Department of Materials Engineering, Technion—Israel Institute of Technology, Haifa 32000, Israel
  2. DND-CAT Synchrotron Research Center, Northwestern University, APS/ANL Sector 5,Building 432A, 9700 South Cass Avenue, Argonne, Illinois 60439-4857, USA
  3. Physics Department, Nuclear Research Centre—Negev, P.O. Box 9001, Beer-Sheva 84190, Israel

Correspondence to: Boaz Pokroy1 e-mail: bpokroy@tx.technion.ac.il

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