Infrared spectra of carbonate apatites: v2-Region bands

The proportions of A and B carbonate ions in a selection of AB carbonate apatites, including hydroxyapatite (CHAP), chlorapatite (CCLAP) and fluorapatite (CFAP), have been obtained Using the out-of-plane bend (v(2)) bands of Fourier transform infrared (FTIR) spectra. Band area ratios (B/A) are ill very good agreement with site Occupancies from single-crystal X-ray Structure refinement; the correlation is linear (1:1) for B/A values ranging Lip to three. Most compositions have v(2) spectra with one band for A carbonate (at 878-880 cm(1)) and one for B (at 870-872 cm(1)). Na-free AB CHAP has a third prominent band at 862 cm(-1), which is assigned to the stuffed channel species (A2), and Na-bearing CFAP has a third band at 864 cm(-1), which is assigned to a second B carbonate environment (B2). The A2 and B2 assignments are based largely oil spectral changes in annealed samples. (C) 2008 Elsevier Ltd. All rights reserved.