Crystallization and sintering characteristics of chemically precipitated hydroxyapatite nanopowder

Hydroxyapatite (HAp) nanopowder was synthesized using a modified chemical precipitation route. Dried HAp gel powder was almost in amorphous state with very low crystallinity as prepared, showing fine a particle size of ∼50-100nm. Due to the enhanced surface area HAp nanopowder showed high sintered density at 1000°C. The Ca/P ratio in powder preparation was varied and the amount of each HAp and β-TCP phase was analyzed using a quantitative X-ray diffraction. The powder with a Ca/P ratio of 1.70 showed the formation of the lowest β-TCP content, while that of 1.75 showed the formation of a CaO phase as well as β-TCP. By using a modified chemical route and varying chemical compositions sintering and β-TCP phase formation behavior of HAp powder could be successfully controlled for artificial hard tissue applications.