Effect of Stabilised ZrO2, Al2O3 and TiO2 on Sintering of Hydroxyapatite

In this work, the hydroxyapatite was prepared from cortical bone after calcination at 700°C during 1 hour. In order to improve mechanical properties of HA, 5 wt% of the ZrO2 (stabilized with 12.0 wt% CeO2), Al2O3 and TiO2 were added to HA powder as a reinforcing phase. All the powders were sintered at 1300°C for 2 hours. The XRD was utilized to identify the phases composition. It was found that the initial calcined powder is hydroxyapatite with the following chemical composition Ca5(PO4)3OH. In addition, the phenolphthalein test has put into evidence the existence of free CaO. For powders containing ZrO2, the XRD spectra has showed a little percent of formed b-tricalcium phosphate (b-TCP); the HA was decomposed to (b-TCP) and CaO which forms with ZrO2 the calcium zirconate (CaZrO3). Nevertheless, in powders containing TiO2, the XRD spectra showed that a partial decomposition of HA to b-TCP was occurred with formation of calcium titanium oxide (CaTiO3). However, for powders containing Al2O3, a nearly full decomposition of HA to b-TCP was occurred, the free Al2O3 was present. Finally, it has been found that HA composites containing a large amount of b-tricalcium phosphate are resorbale than HA composites containing a small amount of b-TCP and they were not well densified. The microhardness values of HA- ZrO2 composites were greater than those of HA- Al2O3 and HATiO2 composites.