Theoretical and experimental characterization of Bİ and GD co-doped hydroxyapatites

Within the scope of the thesis, the effects of bismuth (Bi) and gadolinium (Gd) additions on the structural, thermal, and electronic properties of hydroxyapatite (HAp) were systematically investigated. HAp samples were synthesized using calcium nitrate tetrahydrate, bismuth (III) nitrate pentahydrate, gadolinium (III) nitrate hexahydrate, and diammonium hydrogen phosphate, followed by calcination at 900 °C. Advanced techniques such as XRD, FTIR, Raman, SEM, and TGA/DTA were utilized in the characterization studies. The electronic structures were investigated using theoretical calculations, and the effects of the dopant elements on the band gap were evaluated. According to the findings, Bi and Gd doping reduces the band gap of HAp, thereby increasing its electronic conductivity and enhancing the material's potential for biomedical, electronic, and catalytic applications. At the same time, the dopants caused shrinkage in the crystal structure, resulting in a decrease in lattice parameters and unit cell volume. Parallel to these structural changes, an increase in density values was observed, which was attributed to the high atomic masses of the dopant elements. LAC (linear absorption coefficient) values decrease with photon energy, and the type and ratio of additives directly affect this parameter. The results obtained demonstrate that the mechanical, thermal, and electronic properties of doped HAp materials can be controlled, thereby supporting their potential use in advanced technology applications.