Preparation of high homogeneity BaO-TiO2-SiO2 gel

In BaO-TiO₂-SiO₂ system, crystallization from various gel by heating depended on the sol-gel processes and gel homogeneity. Through the condensation reaction of Si(OAc)₄ and TiAcAc(OⁱPr)₃ in tetrahydrofuran solvent, homogeneous TiO₂-SiO₂ sol with oligomers of relatively large molecular weight was obtained. The gel prepared by mixing the binary sol, Ba(OAc)₂, and Si(OMe)₄ was the most homogeneous in term of suppression of crystallization. By heating the above gel, only Ba₂TiSi₂O₈ crystal appeared, which was observed in a melt quenched glass. In the case of the gels made by other sol-gel processes, TiO₂ or BaTiO₃ crystal was first observed from the heated gels prior to the precipitation of Ba₂TiSi₂O₈.