Figure 8. Rietveld refinement fit of powder XRD data of hydroxyapatite (HAp) ( a ), 7ZnHAp ( b ), Figure 8. Rietveld refinement fit of powder XRD data of hydroxyapatite (HAp) ( a ), 7ZnHAp ( b ), and and 20ZnHAp ( c ). The blue line marks the experimentally observed pattern, while the gray line marks 20ZnHAp ( c ). The blue line marks the experimentally observed pattern, while the gray line marks the the calculated diffraction pattern. The positions of the calculated Bragg peaks were marked with the calculated diffraction pattern. The positions of the calculated Bragg peaks were marked with the vertical lines. The difference pattern between observed and calculated patterns was represented by the vertical lines. The difference pattern between observed and calculated patterns was represented by gray line at the bottom of the figure. ZnHAp: zinc-doped the gray line at the bottom of the figure. ZnHAp: zinc-doped hydroxyapatite. The positions of the diffraction lines of the hexagonal hydroxyapatite (ICDD-PDF No. 9-432) are represented by the vertical lines. The difference between experimental data and those calculated is represented by the gray line at the bottom of the figure. It was noted that between the experimental