Crystal structure analysis of selenium-doped hydroxyapatite samples and their thermal stability

The aim of this study is to obtain more information about the fine crystal structure of selenium-doped hydroxyapatite (Se-HA) and investigate the effect of Se doping on the thermal stability of HA. Se-HA samples with different Se/P ratios were synthesized by the chemical precipitation method. The physicochemical properties of the powders were characterized by X-ray fluorescence spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The results indicate that selenite and a small amount of carbonate co-incorporate into the well-crystallized samples by substituting for phosphate groups. Rietveld refinement was performed to further analyze the crystal structure and determine the crystal structure model of the Se-HA samples. Se incorporation leads to an increase of the a lattice parameter and a decrease of the c lattice parameter of the crystal lattice. The thermal stability of the Se-HA powders during sintering is also discussed. Doping the HA structure with a small amount of selenium improves the thermal stability of HA. Compared with HA, the Se-HA samples with Se/P ≤ 0.05 doping are more stable after heat treatment without any impurities, which makes these materials promising for bone repair materials.