ESR and IR studies of carbonate-containing hydroxyapatites

Synthetic carbonate-containing and carbonate-free hydroxyapatites (CO sub(3)-HA and CO sub(3)-free HA) have been investigated using ESR and IR absorption, together with X-ray diffraction and chemical analyses. Comparison of the IR spectra between super(13)C-enriched super(13)CO sub(3)-HA and super(12)CO sub(2)-HA prepared at 100 degree C and at high pH suggested that the carbonate substitutes for PO sub(4) but not for HPO sub(4). The substitution of CO sub(3) for PO sub(4) in this case resulted in elimination of hydroxyl ions in a hexad axis.