FT-IR and XRD investigations on sintered fluoridated hydroxyapatite composites

Sintered fluoridated hydroxyapatite (FHA) composites were synthesized by calcination at 700 °C for 2 h. The phase changes of the sintered FHA composites have been studied by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR). The effects of the calcination temperature and the presence of calcium fluoride (CaF2) on the sintered FHA composites were examined. The expanded (300) XRD reflections of sintered FHA composites were significantly different from the uncalcined hydroxyapatite (HA). The XRD reflection peaks of sintered FHA composites gradually shifted to a higher-angle direction when CaF2 increased. The shift of peaks indicates the a-axis lattice parameter reduction as a result of the calcination process and the substitution of OH by F. The uncalcined composite materials were stable in OH vibrational groups and showed neither OH·F·OH nor OH·F hydrogen bonds. The sintered FHA composites showed FHA phase. With the increase of CaF2 wt.%, the OH·F·OH and then OH·F hydrogen bonds of sintered FHA composites were forming.