Ethanol-based sol-gel synthesis of nano-crystalline hydroxyapatite with different calcium phosphorus ratios (Ca/P)

One of the easy ways to prepare nanocrystalline hydroxyapatite (nano-HAp) is the sol-gel method that due to its unique advantages compared to conventional methods, has raised research interest among scientists. The purpose of this study was to investigate the properties of nano-HAp powders which were synthesized by ethanol-based sol-gel method with stoichiometric ratio of Ca/P = 1.67 and comparing it with closer ratios of 1.5 and 1.6. To do so, we used the aqueous solution of phosphorus pentoxide (p₂0₅, MERCK) and four-watered calcium nitrate (Ca (NO₃)₂.4H₂O, MERCK) in ethanol. The resulted nano-powders and sintered pellets made of it were analysed and compared with X-ray diffraction analysis (XRD). Also, the sintered pellets’ bioactivity in simulated body fluid (SBF) solution was examined by SEM. In powders which were calcined at the temperature of 600 °C, the most amorphous phase (49%) in comparison to Ca/P = 1.5 was observed. After sintering, the main phase of 1.67 ratio was hydroxyapatite (HAp) and the main phase of 1.5 ration was β-TCP, although in 1.6 ration a composite of HAp and β-TCP was observed. According to the results, sol-gel method for producing nanocrystalline HAp was an appropriate method; in addition, compared with the different ratios of Ca/P, the stoichiometric nanocrystalline may have better bioactivity.