Chiang Mai Journal of Science

Nanocrystalline hydroxyapatite (HAp) powders were successfully synthesized by a polymerized complex method and calcination at 750, 800, 900 and 1,000^oC for 12 h. The specific surface areas of the calcined powders obtained by BET adsorption technique were 1.83 - 42.82 m²/g, depending on the calcination temperature and soaking time. The phase composition of the calcined powders was studied by X – ray diffraction (XRD) technique. The XRD results confirmed the formation of  HAp phase with a small trace of  β–TCP phase. With increasing calcination temperature, the crystallity of the HAp increased, showing the hexagonal structure of HAp with the lattice parameter a in a range of 0.9351 – 0.9446 nm and c of 0.6843 - 0.6906 nm The particle sizes of the powder were found to be 16 – 125 nm and as evaluated by the XRD line broadening technique and were 44 – 1,044 nm as obtained from the BET surface area data. The chemical compositions of the calcined powders were characterized by Raman and FTIR spectroscopies. The Raman spectra showed the phosphate vibration mode (ν₁(PO₄)) at 963 cm^-1  for all the calcined powders. The peaks of  the phosphate carbonate and hydroxyl vibration modes were observed in the FTIR spectra for all the calcined powders. The morphology of  the powders was spherical of  size less than 200 nm, as revealed by TEM.  Increasing the calcination temperature resulted in the transition from polycrystalline to single crystalline phase of  the HAp, as clearly confirmed by the analysis of  TEM diffraction patterns.