Figure 14. The same 2nd echo of hydroxyapatite (HAp) ( a ), 7ZnHAp ( b ), and 20ZnHAp ( c ) samples Figure 14. The same 2nd echo of hydroxyapatite (HAp) ( a ), 7ZnHAp ( b ), and 20ZnHAp ( c ) samples selected for investigation. ZnHAp: zinc-doped selected for investigation. ZnHAp: zinc-doped hydroxyapatite.