Synchrotron X-ray Absorption Spectroscopy study of local structure in strontium-doped hydroxyapatite

In this work, Sr-doped hydroxyapatite (HAp) materials were prepared by a sol-gel method and their overall structure, investigated by X-ray diffraction, showed a mixture of hydroxyapatite and β-calcium phosphate (TCP) crystals. The Sr L3-edge XANES spectra were measured and compared with simulated XANES spectra obtained from the FEFF8.2 program in conjunction with first-principles calculations by density functional theory (DFT). Based on the good agreement between the experimental and calculated local environment results, the conclusion could be drawn that Sr substitutes on the hydroxyapatite Ca1 site close to the phosphate (-PO4) group capable of bonding with living osseous tissues, while the substitution of Sr2+ cations at the other sites was unlikely in bone-based compounds.