Investigation on Preparation Factors for Fluorhydroxyapatite by an Aqueous Precipitation Method

The nanosized fluorhydroxyapatite (FHA) were synthesized by an aqueous precipitation method. The effects of synthesis temperature, molar ratio of NH4F to Ca(NO3)2·4H2O in the initial reagents[n(F–)/n(Ca2+)] and the pH value on the fluoride substitution were investigated. The phase composition and the change of crystal structure were characterized by X―ray diffraction (XRD) and Fourier transform infrared spectroscope (FT―IR). The morphology of FHA was observed by Transmission electron microscope (TEM). The results show that crystal lattice parameters and bond energy make changes by incorporation of F– ion in the structure. The size and aspect ratio of FHA crystals increase as the precipitation temperature and fluoride concentration. The phase composition of FHA is mainly controlled by the pH value. Considering the possibility of a competition between OH– and F– for occupation of the OH–site, high pH value isn’t conductive to the fluoride substitution.