Role of titanium in TiO2: SiO2sol–gels: an X-ray diffraction study

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Abstract
Transmission X-ray diffraction has been used to study a series of powdered silica: titania sol–gel glasses with titania contents ranging from a ‘pure’ silica sample through to high titania levels where phase separation is predicted to occur. Analysis of the data reveals a change in second- and third-neighbour coordination numbers with increasing Ti content and confirms that for low titanium contents the sol–gels are atomically mixed. The lower titanium content sol–gels have also been studied as spun thin films using shallow-angle X-ray diffraction. Comparison with the transmission studies shows an increase in disorder in the silica network when the material is in the form of a coating rather than in the bulk. An increase in the number of Si–O–H bonds is also suggested.