Matéria (Rio de Janeiro)
On-line version ISSN 1517-7076
MOREIRA, E.L.; ARAUJO, J.C.; MORAES, V.C.A. and MOREIRA, A.P.D.. Analysis of a carbonated hydroxyapatite by X ray difraction using the Rietveld method. Matéria (Rio J.) [online]. 2007, vol.12, n.3, pp.494-502. ISSN 1517-7076. http://dx.doi.org/10.1590/S1517-70762007000300010.
The crystal structure of hydroxyapatite (HAP) is known to permit a great variety of substitutions anionic and cationic. Among these substitutions, the insertion of CO32- group is emphasized for its importance in biomaterial applications. In this work, a synthetic sample of nanostructure carbonated hydroxyapatite (CHA) was submitted to thermal treatment at 500ºC for 6 h. Later the structural, microstructural aspects and crystallite size were analyzed for X-Ray diffraction by the Rietveld method (program FULLPROF). The refinement of structural parameters, particularly the atomic occupancy factors, indicated a distribution CO32- ions between PO43- and OH- sites, occurring a great insertion in the phosphate site. The unit cell parameters of CHA compared to HAP pattern (ICSD 26-204) showed a decrease in the a-b parameter and an increase in the c parameter. The Rietveld refinement method was used for to estimate quantitavely the inclusion of foreign ions in the HAP structure. The crystallite size in the crystallography axis directions suggests an equiaxial morphology. The content of the carbonate íon for the sample obtained by the refinement of the occupancy factors was 10,7% in good agreement with the 12,8% content by the Temperature Programmed Dessorption (TPD).
Keywords : Carbonated hydroxyapatite; Rietveld refinement; X-Ray diffraction; Microstructural analysis and Crystallite size.