Raman Spectroscopy Investigation of Nano Hydroxyapatite Doped with Yttrium and Fluoride Ions

In this study, nano hydroxyapatite doped with yttrium (2.5, 5, and 7.5 mol%) and fluoride (2.5 mol%) ions were synthesized by precipitation method and sintered at 900°C, 1100°C, and 1300°C. Raman spectroscopy was applied to track the structural modifications in pure and doped hydroxyapatites. The results showed that the main characteristic band of pure hydroxyapatite at 963 cm^?1 was not affected significantly by ion doping but exhibited higher intensity with increasing sintering temperature. Due to fluoride substitution, the 1048 and 1034 cm^?1 bands of pure hydroxyapatites appeared with a wavenumber shift in the spectra of ion-doped hydroxyapatites. The 333 cm^?1 band of pure hydroxyapatite disappeared and an additional calcium–fluor bond at 322 cm^?1 was observable in ion-doped hydroxyapatites. Two fluorescence bands at 770 and 697 cm^?1, which were also observed in the spectra of pure hydroxyapatites, shifted to higher wavenumbers in the spectra of ion-doped hydroxyapatites. This was considered to result from the perturbation in the hexagonal structure of hydroxyapatite due to yttrium and fluoride codoping.