Modulating the anion ordering in apatites

• Hydroxyapatite constitutes the main inorganic part of the skeleton, and since the beginning of the seventies, synthetic apatite has been used in implants. The physical properties of this crystalline material are directly dependent on its atomic arrangement. If a better understanding of apatite chemistry is sought, important for e.g. the development of new implant materials, it is absolutely crucial to know the detailed structural chemistry of the apatites. It is in this context that this thesis fits.X-ray and electron diffraction techniques in combination with high resolution transmission electron microscopy have been used for the characterisation of the new compounds and the combination of these techniques has been particularly useful.Common for the studies presented is that they focus on the anion ordering along the hexagonal axis within the apatite framework, this being responsible for the new structures discovered:The crystal structure of completely dehydrated hydroxyapatite, oxyapatite, has been elucidated from HREM images.Partially dehydrated hydroxyapatite is shown to be triclinic.The sulfo- and seleno analogues of oxyapatite have been prepared and their structures refined from X-ray diffraction data.A new commensurate modulation along c is found for iodo-oxyapatite.A new incommensurate modulation along c is found for cadmium-bromoapatite.As a consequence of the structural chemical investigations performed, the hypothesis arose that it might be possible to manipulate the hydroxide ion ordering in hydroxyapatite achieving a piezoelectric apatite. This hypothesis has recently been confirmed. This new apatite may find important applications in the development of new, biocompatible, implant materials.

Ämnesord

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

Nyckelord

oorganisk kemi

Inorganic Chemistry

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