Characterization of calcium, strontium, barium and lead hydroxyapatites: X-ray diffraction, photoelectron, extended X-ray absorption fine structure and MAS NMR spectroscopies

Calcium, strontium, barium and lead hydroxyapatites have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS),extended X-ray absorption fine structure (XAFS) and solid state NMR. XPS analyses s howed that the binding energies of P 2s or P 2p and O 1s of all hydroxyapat ites, XRD of which matched to the corresponding JCPDS data, were essentiall y identical and were not influenced by those divalent cations. In contrast, it was revealed that the nearest neighbour distances between divalent cati ons and oxygen determined by XAFS and the chemical shifts of H-1 and P-31 N MR were strongly influenced by each divalent cation in hydroxyapatites.