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.