ROLE OF TITANIUM IN TIO2-SIO2 SOL-GELS - AN X-RAY-DIFFRACTION STUDY

Transmission X-ray diffraction has been used to study a series of powd ered silica:titania sol-gel glasses with titania contents ranging from a 'pure' silica sample through to high titania levels where phase sep aration is predicted to occur. Analysis of the data reveals a change i n 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 s tudied as spun thin films using shallow-angle X-ray diffraction. Compa rison with the transmission studies shows an increase in disorder in t he silica network when the material is in the form of a coating rather than in the bulk. An increase in the nun;ber of Si-O-H bonds is also suggested.