Differentiation between hydroxyapatite and β-tricalcium phosphate by means of μ-raman spectroscopy

We present a comparative study of the Raman spectra of polycrystalline beta-tricalcium phosphate (beta-TCP) and hydroxyapatite (HA) over their whole optical frequency range. Due to their structural differences, Raman scattering permits to differentiate between these two calcium phosphates, not only through the detection of vibrational modes associated with the OH- group of hydroxyapatite, but also by comparing the bands arising from internal PO43- modes. The widths of the Raman-scattering bands associated with PO43- bond-bending modes and the frequency gap between them are characteristic features that can be used to distinguish between P-TCP and HA. The method is used to identify a HA layer a few microns thick which precipitates on the surface of TCP-wollastonite eutectic soaked in simulated body fluid. (C) 1998 Elsevier Science Limited. All rights reserved.