Influence of hydrolysis water content on the microstructure of BaTiO3 xerogels prepared from high concentration metal alkoxide solutions

Optically clear and partially crystallized barium titanate (BaTiO3) monolithic xerogels were prepared by hydrolyzing the high concentration precursor solutions (1.1 mol/L) of metal alkoxides with water vapor to have different hydrolysis water contents (H2O/Ba-alkoxide mole ratio (r(w)) = 2.5-7.0). The microstructural changes of the xerogels have been studied by TEM, XRD and nitrogen adsorption/desorption analysis. The crystallite size of the xerogels was found to increase consecutively with increasing r(w), while the average pore size showed no substantial increase until r(w) = 5.0 and it grew rapidly for r(w) > 5.0. The influence of r(w) on the microstructural development of the xerogels with heat-treatment was also discussed.