A simple sol-gel technique for preparing hydroxyapatite nanopowders

HA powder was prepared using a sol-gel method with phosphoric pentoxide (P2O5) and calcium nitrate tetrahydrate (Ca(NO3)2·4H2O). The effect of sintering temperatures on crystalline degree and composition of the HA phase, and also the effect of aging times on crystal size of the HA powder were studied using XRD and TEM. It was found that at sintering temperatures ranging from 600 to 900 °C, the dominant phase in the powders was HA with small amounts of calcium oxide and β-tricalcium phosphate (β-TCP) at 800 and 900 °C, and only HA phase was observed at 600 and 700 °C. 10-15 nm HA powders were obtained using this technique. This technique has an advantage over other sol-gel methods in more simple and shorter time because of no requiring pH value control and long hydrolysis time.