Synthesis and characterisation of hydroxyapatite and fluorapatite

Hydroxyapatite (HA) and Fluorapatite (FA) were synthesised by a wet process and a solid reaction, respectively. They were characterised by X-ray diffraction (XRD), Fourier transform infrared (FTLR) spectroscopy, and transmission electron microscopy (TEM). The resulting HA particles were platelet shaped with a size of 20 × 70 nm, and FA particles were of a similar shape but twice as large as those of HA. Both HA and FA powders were pressed into discs and sintered. The sintering behaviour and biaxial flexural strength of HA and FA discs which has been sintered at various temperatures were studied. With increasing sintering temperature, HA decomposed at 1400°C, but no decomposition of FA was found even at 1500°C (maximum available). The peak biaxial flexural strength of both HA and FA was approximately 80 MPa and this was achieved when the specimens were sintered at 1200°C and 1400°C, respectively. It was discovered that the microstructure of both HA and FA changed dramatically with the sintering temperature. It seemed that the changes of microstructure and strength were coupled.