Low-temperature laser Raman spectroscopy of synthetic carbonated apatites and dental enamel

Abstract

A range of synthetic carbonated apatites and human dental enamel have been studied at low temperatures (50 K) by laser Raman spectroscopy. The widths of the Raman spectral bands of hydroxyapatite were significantly reduced at low temperatures with the appearance of several peaks unobserved at room temperatures. The number of observed phosphate and hydroxyl ion Raman peaks was consistent with the space group P6₃. Spectra of carbonated apatites were not further resolved at low temperatures and Raman peak broadening due to loss of long-range translational order in the apatite structure was linearly correlated with the carbonate content of the sample. The same Raman peak broadening occurred in the spectrum of dental enamel. The number of carbonate bands in the Raman spectrum of carbonated apatites indicated that carbonate exists in two crystallographically distinct sites of different symmetry within the apatite structure.