An atomic-scale study of the role of titanium in TiO2:SiO2 sol-gel materials

Neutron diffraction data is used to reveal details of the effect of adding titania to a silica-based sol-gel, including a first direct observation of the TiO correlation. At low Ti contents the data are consistent with the 4-fold oxygen coordination derived from NMR. Even at these concentrations the silica network is shown to have been affected significantly, with bond-length distributions being narrowed, and with a high level of network-OH indicating a qualitative change in the mesoscopic structure associated with interfacial surfaces. Data on a phase separated sample supports the conclusion that the network-OH is associated with the phase separation process.