Nanocrystalline fluorine-substituted hydroxyapatite [Ca5(PO4)3(OH)1-xFx (0 ⩽ x ⩽ 1)] for biomedical applications: preparation and characterisation

Several fluorine-substituted hydroxyapatite ceramics with the general chemical formula Ca₅(PO₄)₃(OH)_1-xF_x (0≤x≤1), where x=0.0 (hydroxyapatite; HA), x=0.41 (fluorhydroxyapatite; FHA1) and x=0.69 (fluorhydroxyapatite; FHA2) and x=0.98 (fluorapatite; FA), were synthesised via pH-cycling method. The powders were characterised by using scanning electron microscope, transmission electron microscopy (TEM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD) and F-selective electrode. The TEM micrographs showed that the increasing of fluoride ion concentration will cause a reduction in the aspect ratio of the produced crystallites. The XRD analysis of the calcined powders showed that all of the synthesised powders were pure and their XRD patterns were similar together. Eventually, the FTIR results suggest that the fluorine has substituted instead of hydroxyl groups in the fluoridated hydroxyapatite samples.