Figure 1. FTIR spectra of synthesized apatite at different temperature. (b) Table shows the peak positions of different assignments related to PO43- and OH bonds at different temperatures.
Across all temperatures, we detected the high intensity bands in the range 561-606 cm-1 that are assigned to the ν4” out of plane and ν4”’ bending modes of the PO43- unit. Moreover, the intense infrared bands between 1023-1099 cm-1, which are attributed to the PO43- ν3’ and ν3”’ stretching vibrations, were observed. Furthermore, infrared bands between 960-965 cm-1, known as the PO43- ν1 symmetric stretching vibrational mode were observed.
Weak infrared peaks were also seen at 865-870 cm-1 for the precipitate formed at 90C and for the HAp Captal® R spectra respectively, which corresponds to the carbonate groups (CO32-). This confirms the previous findings of Okazaki37 who stated that the 875 cm-1 corresponds to CO32- groups substituted with PO43- tetrahedron (type B carbonated apatite), and when shifted to a lower frequency, it indicates higher degree of fluoridation. This is due to the conformation of the carbonate groups in the lattice are significantly affected by the F- content.
Table 1 : Peak positions of different assignments related to PO43-, OH, and CO32- bands at different temperatures.