Biomimetic apatite coatings were obtained by soaking chemically treated titanium in SBF with different HCO₃^- concentration. XRD, FTIR and Raman analyses were used to characterize phase composition and degree of carbonate substitution. The microstructure, elemental composition, and preferred alignment of biomimetically precipitated crystallites were characterized by cross-sectional TEM analyses. According to XRD, the phase composition of precipitated coatings on chemically pre-treated titanium after exposure to SBF was identified as hydroxyl carbonated apatite (HCA). A preferred c-axis orientation of the deposited crystals can be supposed due to the high relative peak intensities of the (0002) diffraction line at 2Theta = 26° compared to the 100% intensity peak of the (2131) plane at 2Theta = 32°. The crystallite size in direction of the c-axis of HCA decreased from 26 nm in SBF5 with a HCO₃^- concentration of 5 mmol/l to 19 nm in SBF27 with a HCO₃^- concentration of 27 mmol/l. Cross-sectional TEM analyses revealed that all distances correspond exactly to the hexagonal structure of hydroxyapatite. The use of an auto-correlation method indicates that most of crystallites c-axes are distributed in a cone with an apex angle of about 30° around a preferential orientation perpendicular to the titanium surface. The HCO₃^- content in SBF also influences the composition of precipitated calcium phosphates. Biomimetic apatites were shown to have a general formula of Ca10-x-yMgy(HPO4)x-z(CO3)z(PO4)6-x(OH)2-x-w(CO3)w/2. According to FTIR and Raman analyses, it can be supposed that as long as the HCO3- concentration in the testing solutions is below 20 mmol/l, only B-type HCA (0 < z < 1; w = 0) precipitates. At higher HCO₃^- concentration, it can be assumed that AB-type HCA (z = 1; 0 < w < 1) forms.

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