PRESSURE-INDUCED CRYSTALLINE-TO-AMORPHOUS TRANSITION IN HYDROXYLAPATITE

Hydroxylapatite, prepared by the reaction of an aqueous suspension of Ca(OH)(2) with H3PO4 at pH >7 and sintered at 700 degrees C was subjec ted to various pressures in a Bridgman anvil apparatus, and the retrie ved material was examined by X-ray diffraction (XRD), Fourier transfor m infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods. The studies showed that the crystalline hydroxylapatite trans forms irreversibly to an amorphous phase 2 GPa. The transformation occ urs through an intermediate phase and is completed at around 10 GPa pr essure.