The effects of zinc oxide on the sinterability of hydroxyapatite

In the present work, the hydroxyapatite (HA) powders were synthesized via wet chemical method. The phase formation as well as the morphology of the synthesized HA powders were studied. Then the sinterability of hydroxyapatite (HA) powders doped with zinc oxide (ZnO) ranging from 0.1 to 1.0 wt% was investigated. The ZnO-doped HA powders were obtained by incorporating ZnO into the synthesized HA powders via ball milling for 1 hour. The green samples were prepared and sintered in air at temperatures ranging from 1100°C to 1250°C. The sintered samples were characterized to determine the phase stability, bulk density, microstructure and grain size, hardness and fracture toughness. XRD analysis revealed that there were no secondary phases detected for all the ZnO-doped and undoped HA samples throughout the sintering regime employed. It was found that all the ZnO-doped HA achieved > 98% relative density when sintered at 1200°C while undoped HA could only attained highest value of 97% at the same temperature. Higher content of ZnO addition appeared to be advantageous to the densification of HA. Besides, the addition of 0.5 wt% ZnO into HA was found to be the most effective in enhancing the mechanical properties of HA. This sample possessed the highest hardness and fracture toughness of 4.76 GPa and 1.34MPam
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as compared to 4 GPa and 1.01MPam
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for undoped samples at sintering temperature of 1200°C.