VIBRATIONAL PROPERTIES OF CALCIUM-PHOSPHATE COMPOUNDS .2. COMPARISON BETWEEN HYDROXYAPATITE BETA-TRICALCIUM PHOSPHATE

A comparison between Raman spectra of polycrystalline Ca-10(PO4)(6)(OH )(2) and beta-Ca-3(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 spe ctra allow us to establish a distinction between these two calcium pho sphates. Besides the presence of peaks associated with vibrations of t he 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 b etween hydroxyapatite and beta-Ca-3(PO4)(2).