Synthesis of different bismuth titanates and ordered Bi-Ti-O nanocomposites based on opal matrices

Abstract

Bismuth titanates of different composition and 3D nanocomposites based on opal matrices and bismuth titanates of different structure types have been synthesized by sol–gel and alkoxide methods with the use of polyhydric alcohols. The suggested procedure for synthesis of bismuth titanates Bi₁₂TiO₂₀ with a sillenite structure and Bi₂Ti₂O₇ with a pyrochlore structure and layered titanates Bi₄Ti₃O₁₂ makes it possible to decrease the temperature of the onset of formation of a target product in powders and a 3D nanocomposite based on opal matrices and to reduce the synthesis time. It has been revealed that the aging of the initial sol has an effect on the phase composition of bismuth titanates. It has been found that formation of the bismuth dititanate phase with a pyrochlore structure in the pores of opal matrices (nanoreactors) becomes dominating whatever the Bi₂O₃/TiO₂ ratio is (2 : 3 or 1 : 2), which is associated with the effect of the size factor on the stability of the forming phases. It has been shown that the existence range of metastable Bi₂Ti₂O₇ and Bi₂SiO₅ forming as nanoparticles can be extended from 20 to 1000°C through confinement of the reaction zone of the sol–gel synthesis in the pores of the opal matrix.