Properties of hydroxyapatite crystallized from high temperature alkaline solutions

Hydroxyapatite was prepared from alkaline solutions at 95 degrees C by the method of slow titration in an atmosphere of nitrogen. The crystals were ripened under reflux for various periods of time, and then characterized by X-ray diffraction, infrared analysis, transmission electron microscopy, differential thermal analysis, thermogravimetric analysis, surface area measurements and chemical analysis. The obtained crystals are pure apatites with stoichiometric Ca/P ratio. The phase composition of the prepared powders remains unchanged after heating at 900 degrees C during 2 h. The lattice constants of maturated powders were in excellent agreement with ASTM 9-432 diffraction file data for the hydrohxyapatite. Ripening under reflux improved lattice ordering but did not have a marked effect on the Ca/P ratio. Crystallite size and morphology significantly changed during the first day of refluxing following synthesis.