Investigation on High-temperature decomposition characteristic of hydroxyapatite

Hydroxyapatite (HA) has been widely used in clinical field because of its excellent biocompatibility. However, its poor thermal stability limits its application. In present paper, the decomposition characteristics of both nano-sized HA powder prepared by precipitation method and its sinters at the temperature from room temperature to 1500°C in the air were studied. X-ray diffractometer (XRD), High-temperature Raman spectroscopy, High-temperature differential scanning calorimeter (DSC) and Cell culture work were used to investigate their decomposition characteristics. The results show that HA gradually releases its OH^- ions from 1000°C and decomposes into β-tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP) when the heating temperature is higher than 1350°C. β-TCP changes into α-TCP at about 1450°C, which remains until the sinter cools to the room temperature. The decomposed sinter reconstitutes to HA again under a slow cooling rate and in a specific atmosphere. The osteoblast on the surface of decomposed sinter is less than that on the undecomposed one.