Structural Analysis of Silver Doped Hydroxyapatite Nanopowders by Rietveld Refinement

Silver doped hydroxyapatite (AgHAP) nanopowders have been receiving great attention in orthopedic and dental implant applications owing to high bioactivity and antimicrobial properties. In the present study, AgHAP (Ca 10−x Ag x (PO 4 ) 6 (OH) 2 where x = 0.01–0.05) nanopowders were synthesized by setting the atomic ratio of Ag/(Ca+Ag) at 1, 2, 3, 4, 5% and (Ca+Ag)/P molar ratio at 1.72 using sol–gel route. XRD and FTIR were employed to characterize phase and molecular structures of nanopowders, respectively. Crystallographic information of nanopowders was obtained using Rietveld refinement technique. It was observed that with the increase in doping percentage of Ag, AgHAP nanopowders remained biphasic i.e. composed of HAP and Ag 3 PO 4 phases, whereas, inter-atomic distance between some selected atoms decreased, lattice parameters of HAP increased, lattice parameter of Ag 3 PO 4 decreased and crystallite size of both HAP and Ag 3 PO 4 phases increased. Crystallinity was maximum (60.1%) in nanopowder having Ag concentration of 3%. Type 2 Ca atoms were maximally replaced by Ag atoms. Difference in nominal and refined (Ca+Ag)/P molar ratio was observed. FTIR confirmed the formation of carbonated apatite in all nanopowders. Hence, this study presents a judicious approach to deeply analyze the influence of silver concentrations on structural parameters of AgHAP nanopowders.