Metal oxide sols can be prepared from metal alkoxides M(OR)4 by hydrolyzation

which has been widely used in synthesis of nano-porous ceramic membranes by sol-gel method. Polymeric TiO2-ZrO2 sols were prepared by controlled hydrolyzation of the mixture of titanium isopropoxide and zirconium n-propoxide in isopropanol. The formation of TiO2-ZrO2 sols from the initial reactant mixtures with a molar ratio of Ti(i-OC3H7)4:Zr(n-OC3H7)4:H2O:i-C3H7OH=0.9:0.1:m:30 (m=1.8

2.0

2.2) was investigated by small angle X-ray scattering (SAXS). The effects of the molar ratio of water to metal alkoxides H2O/M(OR)4 (M=Ti+Zr) in the initial reactant mixture

reaction temperature and Zr(n-OC3H7)4 on formation of TiO2-ZrO2 sols were discussed. When the molar ratio of H2O/M(OR)4=1.8

a few colloidal particles form. When the molar ratio of H2O/M(OR)4 is in the range of 2.0-2.2

the colloidal particles in TiO2-ZrO2 sols have a mass fractal structure with a fractal dimension of 1.2 ≤ Dm < 1.4. As the molar ratio of H2O/M(OR)4 increases from 2.0 to 2.2

the duration of colloidal particle formation becomes shorter

the size and fractal dimension of colloidal particles increase

and the stability of TiO2-ZrO2 sol decreases. Furthermore

the mixture of[Ti(i-OC3H7)4+Zr(n-OC3H7)4] hydrolyzes faster than Ti(i-OC3H7)4. TiO2-ZrO2 sol has lower stability than TiO2 sol from the initial reactant mixtures with the same molar ratio of H2O/M(OR)4.