A detailed investigation of the polarized Raman spectrum of monoclinic hydroxyapatite (OHAp) and a careful study of the low frequency infrared spectrum of polycrystalline OHAp, is reported. Most of the spectral details of Raman scattering are consistent with the local pseudo-hexagonal C6 factor group symmetry of OHAp. However, some features, for example the absence of TO-LO splitting for particular E1 phonon geometries and the splitting of the lowest frequency Raman line, are a reflection of the centrosymmetric monoclinic lattice of OHAp. Between 0 and 50cm-1, a temperature-dependent background, having E1 symmetry, and probably associated with OH- disordering flucuations, was observed in OHAp. Both OHAp and FAp displayed low frequency Raman lines which softened with decreasing temperature. However, no evidence for a phase transition was found in either OHAp or FAp in the 12-295 K temperature range.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics