Structure of lead oxyfluorosilicate glasses: X-ray photoelectron and nuclear magnetic resonance spectroscopy and molecular dynamics simulation

X-ray photoelectron (XPS) and 29Si magic angle spinning (MAS)-NMR spectroscopy have been used to examine the chemical states of fluorine, oxygen, silicon and lead atoms in the glasses of composition xPbF2·(100−y−x)PbO·ySiO2 (x=0,5,10,15,20,30 mol%, y=30,50,60 mol%). The analysis of the F 1s spectra indicated that Pb2+ and F− ions are preferentially located among the Si–O skeleton forming ionic Pb–F clusters. The fraction of the bridging (BO) and non-bridging oxygen (NBO) atoms was derived from the O 1s spectra. The network of the fluorine-containing glasses was concluded to depend on the ratio PbO/SiO2; when the ratio PbO/SiO2 was lower than 0.5, not only Pb atoms but also F atoms play a role as network modifiers, while when the ratio PbO/SiO2 is higher than 1.33, part of Pb atoms plays a role as a glass network former.