INITIAL RIETVELD CHARACTERIZATION OF BIOLOGICAL CALCIFICATIONS

X-ray diffraction data has been collected from biological calcific min eral associated with human bone, breast tissue, ureteric calculi, hear t valve, and aorta. All the materials are shown to have a nominal calc ium hydroxyapatite structure and Rietveld analysis has been performed to extract microstructural information. All refinements achieved a fin al R-wp value of <10%. The lattice parameter ranges are a=9.375(3)(bre ast)-9.4316(8)(heart valve), c=6.866(1)(ureteric calculi)-6.899(1)(rib ), and crystallite size range from 40 Angstrom (breast) to 99 Angstrom (ureteric calculi). A correlation between crystallite size estimates from this Rietveld analysis and line profile methods is demonstrated. The results are supported by an infrared study and previous data from alternative techniques. Thus, it is demonstrated that the microstructu re of these materials may be characterised by application of the Rietv eld method. (C) 1997 International Centre for Diffraction Data.