Local atomic structural behavior in amorphous and crystalline diphosphate glasses co-doped by different transition metal ions (Ni2+, Cu2+ and Co2+): XAFS and XRD analysis

In this study, structural features of Na2MxZn1-xP2O7 (M = Cu, Ni and Co; x = 0 and 5 mol %) glass compounds were investigated. X-ray diffraction (XRD) and X-ray Absorption Fine Structure (XAFS) analysis techniques were used to investigate the phase identification and the local atomic environment around Zn element. Non-doped and Cu co-doped compounds show an amorphous glassy character while a tetragonal Na2ZnP2O7 phase was observed in Ni or Co co-doped samples. Fourier-transformed magnitudes of the Extend X-ray Absorption Fine Structure (EXAFS) show a disorder state for pure sample and copper doping compound. On the other hand, nickel or cobalt co-doped compounds show a structural order by the formation of ZnP2O7 sheet. Therefore, transition metals (TMs) co-doped phosphate glass play a key role in the structural order /disorder of the glass compounds, by maintaining and reinforcing or even weakening the network structure.