Hydrothermal Synthesis of Hydroxyapatite with Different Morphologies: Influence of Supersaturation of the Reaction System

In the present study, hydroxyapatite (HA, Ca₅(PO₄)₃OH) with different morphologies, such as nanorods, microspheres, hexagonal prisms, and hollow flowerlike structure, were synthesized via a facile hydrothermal route by adjusting reaction parameters. The as-synthesized samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and high resolution transmission electron microscopy. Furthermore, the saturation index of the reaction systems under different conditions was approximately calculated in order to explore the formation mechanism of HA. The results indicate that both the saturation index and the intermediates presented at the initial stage of the reaction play crucial roles in the formation of HA with different morphologies. These results provide a promising strategy for the tunable synthesis of HA and other nanomaterials