A. Houdi et al., Titanoxane-siloxane eight-membered rings as precursors of anatase/silica and rutile/silica materials, J MAT CHEM, 10(4), 2000, pp. 1001-1005
The eight-membered titanium containing siloxane rings (TiX2)(2)O-4(SiBu2t)(
2) (X = Cl 1, Br 2 or I 3) are efficient single-source precursors to homoge
neous titania-silica material. The ceramic conversions which occur pyrolyti
cally at about 550 degrees C give a mixture of TiO2-SiO2 materials. Differe
ntial thermal and thermogravimetric analysis, X-ray diffraction, vibrationa
l spectroscopy as well as scanning electron microscopy were used to charact
erise the materials. It was found that the nature of the halogen atoms play
a crucial role in the thermal transformation. Thus, after thermal treatmen
t, silica mixed with anatase is obtained from 1 and 3, whereas silica mixed
with rutile is obtained from the brominated precursor 2. The thermal evolu
tion of 1 studied by using Raman and infrared spectroscopies confirms the i
nhibiting effect of SiO2 on the anatase-rutile phase transformation. The mo
lecular route to oxide materials described could represent an alternative t
o the sol-gel process and may offer certain advantages.