Sintering studies of synthesised manganese-oxide-doped calcium phosphate via wet chemical precipitation method

Abstract

The beneficial effects of incorporating small amounts of manganese oxide, MnO2 (0·05, 0·1, 0·3, 0·5 and 1·0 wt%) into biphasic calcium phosphate in promoting sintering and its effect on physical and mechanical properties of the dense sample sintered at 1000–1400°C were investigated. In this work, a wet precipitation method was employed to prepare biphasic calcium phosphate powder. The starting materials of calcium hydroxide and orthophosphoric acid were used in the titration process and the as-synthesised powder was subsequently doped with manganese oxide by wet milling. The X-ray diffraction analysis revealed that the phase present in the as-synthesised powder was predominantly hydroxyapatite. However, upon sintering, all the samples revealed the existence of biphasic calcium phosphate i.e. a mix phase comprising of hydroxyapatite and tricalcium phosphate. The highest relative density of 99·5% was obtained for biphasic calcium phosphate doped with 0·3 wt% MnO2 when sintered at 1400°C. The results also revealed that 0·3 wt% MnO2-doped biphasic calcium phosphate gave a maximum Vickers hardness of 5·14 GPa. On the other hand, 1·0 wt% MnO2-doped biphasic calcium phosphate exhibited highest fracture toughness of 1·32 MPa m1/2 as compared to 0·88 MPa m1/2 for undoped biphasic calcium phosphate when sintered at 1200°C.