Structural Characterization of Low-Sr-Doped Hydroxyapatite Obtained by Solid-State Synthesis

Strontium-substituted Ca10(PO4)6(OH)2 hydroxyapatite (HAp) powders, with Sr wt%
concentrations of 2.5, 5.6 and 10%, were prepared by a solid-state synthesis method. The chemical
composition of the samples was accurately evaluated by using inductively coupled plasma (ICP)
spectroscopy. The morphology of the samples was analyzed via optical microscopy, while structural
characterization was achieved through powder X-ray diffraction (PXRD) and infrared (FTIR) and
Raman spectroscopy. The PXRD structural characterization showed the presence of the Sr dopant in
the Ca1 structural site for HAp with a lower Sr concentration and in the Ca2 site for the sample with a
higher Sr concentration. FTIR and Raman spectra showed slight band shifts and minor modifications
of the (PO4) bands with increasing the Sr doping rate.