Characterization, thermal stability and sintering of hydroxyapatite powders prepared by different routes

Hydroxyapatite (HAP) powder precursors have been used as starting material for biomedical applications, such as synthetic bone graft materials and scaffold for hard tissue engineering. Considering the numerous applications of hydroxyapatite, three different routes for HAP powders preparations was investigated. Two powders were prepared by chemical precipitation reactions at 100 °C and one by mechanochemical reaction. The powders were characterized using chemical analysis, surface area measurements, laser diffraction, X-ray diffraction (XRD) and SEM. The Ca/P ratios were varied from 1.67 to 1.58. The chemical composition, the crystallinity and the agglomeration characters depend on the preparation route. The effect of powder characteristics on the sinterability was investigated. Although, the thermal stability and hence the start of sintering dependents on the Ca/P ratio, the final sintering density and hence the mechanical properties depends on the agglomeration characteristics and the particle size distribution. Hydroxyapatite powder prepared by mechanochemical route have nano-sized crystallites with a uniform smaller agglomerated particle size distribution and have a butter sinterability.