The crystal structure of the synthetic hydroxyapatite with 12.8 (±0,64) wt. % CO3(2-) ion content was analyzed by X-ray diffraction using the Rietveld refinement method employing Pearson VII and pseudo-Voigt functions to fit the X-ray profile. The results obtained for unit cell parameters when compared to pattern hydroxyapatite showed a decrease in the a (=b) parameter and an increase in the c parameter without significant difference between the functions employed. The separation of the anisotropic broadening of reflections originated from unit cell strains indicated that this effect is dominant in reflection line broadening, principally to hkl plans with an interatomic distance lower than 2,24 Å. Modifications in the atomic coordinates of C atom were noted mainly in PO4(3-) (B site) and OH- (A site) sites. The average crystallite size in the crystallography axis directions (002 and 300) suggests equiaxial morphology. The results obtained to CO3(2-) content were 11.72 (±0,64) wt. % to Pearson VII and 13.20 (±0,64) wt. % to pseudo-Voigt function. The refinement of the occupancy factors to C atoms in both sites PO4(3-)(B) and OH- (A) indicated higher insertion in phosphate site than hydroxide site. However, the relative occupancy of the C atom observed in the B site is lower than in the A site.
Carbonated hydroxyapatite; Rietveld refinement; X-Ray
