Hydroxyapatite formation through dissolution–precipitation reaction: Effects of solubility of starting materials

Abstract Hydrothermal processing has been the subject of much attention for hydroxyapatite (HAp) formation because the formed HAp has various morphology. We investigated the effects of solubility of starting materials on the HAp formation and its morphology under a hydrothermal condition. Single crystals of calcite, fluorite and calcium tartrate tetrahydrate with different solubilities were used as starting materials. After hydrothermal processing for 24 h, HAp formed on the surfaces of all the starting materials. Needle-like HAp formed on the surface of calcite and plate-like HAp formed on the fluorite. In the case of the calcium tartrate tetrahydrate, aggregation of nano-sized HAp was observed on its surface. The difference in the solubility of the starting materials might affect the morphology of HAp formed on their surfaces under hydrothermal conditions.