Hydrothermal synthesis and thermal evolution of carbonate-fluorhydroxyapatite scaffold from cuttlefish bones

Phase composition, crystal structure and morphology of carbonated fluor/hydroxyapatite synthesized hydrothermally from aragonitic cuttlefish bones were studied by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS). The product of synthesis has been characterized as carbonated fluor/hydroxyapatite with carbonate incorporated inside channel (A-type) and substituted for the PO₄³⁻ group (B-type). The vibration band at 874 cm⁻¹ assigned to bending (ν₂) mode undoubtedly confirmed carbonate substituted for PO₄³⁻ group, while the band at 880 cm⁻¹ was attributed to A-type carbonate substitution. The additional sharp and intense band at 865 cm⁻¹ considered as "non-apatitic" carbonate substitution is not assigned with certainty so far. Evolution of CO₂ from tetrahedral (PO₄³⁻) sites with the increase in heat-treatment temperature is evident by the changes in tetrahedral bond lengths and angles, as obtained by the Rietveld structure refinement. Also, changes in the isotropic temperature parameters for the 2a site point to A-type carbonate incorporation as well. - Highlights: • Thermal evolution of carbonated apatite from cuttlefish bones has been studied. • A-, B- and "non-apatitic"-type of carbonate in apatite structure was determined. • Carbonated fluor/hydroxyapatite transforms into pure fluorapatite at 1300 °C