Investigation of the effects of praseodymium doping on the structural properties of hydroxyapatite: An experimental and theoretical study

Calcium orthophosphates are a group of bioceramics that have been extensively used for medical purposes, especially for hard tissue engineering. More recently, the study and improvement in such bioceramics have made significant contributions to the health and quality of human life. Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is an important member of the calcium orthophosphate family and has high biocompatibility, osteoconductivity, and bioactivity. HAp can be used as an implant material for the damaged part of the human skeleton system because it has a similar chemical composition to natural human bones. For this master thesis, five samples of hydroxyapatite (HAp) doped with praseodymium (Pr) at various amounts (2, 4, 6, 8 and 10 at.%) were synthesized by using the wet chemical route and characterized experimentally by using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) techniques, cytotoxicity test, thermogravimetric and differential thermal analyses. Additionally, all samples were modeled by using the Quantum Espresso software and theoretically characterized by using the density functional theory (DFT). The influence of Pr into the crystal lattice of HAp was observed. While a gradual increase in the crystallite sizes, lattice parameter a and unit cell volume was found, and a gradual decrease in the crystallinity degree was detected. Pr content from 2 to 10 at.% did not affect the thermal stability of HAp. The theoretical results showed that the bandgap energy of HAp decreased steadily from 3.82 eV to 1.32 eV with adding of Pr, and the density of states (DOS) was also affected by Pr content. The cell viability tests showed that among all the as-synthesized samples the best biocompatible properties were found for the sample, which is doped with 10 at.% Pr. Except for the sample having 6 at.% Pr, all the remaining samples were found to be potentially good candidates for biomedical applications.