Vibrational Properties of Calcium Phosphate Compounds. 2. Comparison between Hydroxyapatite and β-Tricalcium Phosphate

A comparison between Raman spectra of polycrystalline Ca10(PO4)6(OH)2 and β-Ca3(PO4)2 is reported. Both compounds exhibit similar Raman spectra, which are dominated by the internal modes of the PO43- tetrahedra. However, several characteristic features of the Raman spectra allow us to establish a distinction between these two calcium phosphates. Besides the presence of peaks associated with vibrations of the OH- group in the Raman spectrum of hydroxyapatite, which are highly sensitive to sample crystallinity, other characteristic features such as the width of the PO43- internal bands can be used to distinguish between hydroxyapatite and β-Ca3(PO4)2.