Abstract: Nano-sized hydroxyapatite (HA) particles were synthesized by sol-gel through water and ethanol based mediums of phosphoric acid (H3PO4) and calcium hydroxide (Ca(OH)2) at pH = 11 for different calcination time (1 h, 2 h, 4 h). The effects of calcination time and solution on the crystallinity, morphology and impurity phases of the HA nanoparticles were examined via Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD). It was found that crystallite size and the fraction crystallinity of the synthesized samples increased with calcination time. According to solution medium, only CaO as impurity was appeared in the water-based solvent, CaO and Ca(OH)2 impurities were appeared in the ethanol-based solvent. The lowest crystallinity was 0.92 and the highest crystallinity was 1.73 respectively, depending on the process parameters. The Ca/P atomic ratio closest to the bone was found as 1.5178. As a result, the employed water-based sol-gel processes for 1 h calcination time was de-termined as the optimum for the formation of nano-sized HA powders using calcium hydroxide and phosphoric acid.''

Key words: bioceramics, hydroxyapatite, calcination time, XRD, sol–gel