Abstract
Spherical Hydroxyapatite was synthesized using a wet chemical method directly. When titrating a calcium hydroxide suspension into a phosphoric acid aqueous solution to which pyrophosphate has been added as a coagulant, aggregates of CaHPO4·2H2O were produced if the synthesis temperature is 40-60°C, and aggregates of CaHPO4 were formed if 70-90°C; and when maintaining these aggregates in a pH7.0 suspension, they changed to spherical HAp after 24 hours of constant stirring. The structure of the sphaerite appeared as aggregate of fine HAp particles. To make sphaerites of HAp, it is thought that aggregates of CaHPO4·2H2O or CaHPO4 must be produced, and when these change into HAp, sphaerites are made by locally increasing the solubility in the surface vicinity of the aggregates.
