Reactivity of Aluminum and Titanium Oxides under the Conditions of the Synthesis of Strontium and Barium Titanates in Water Fluid Media

Strontium and barium titanates deposited on a porous support (α-Al2O3) are synthesized by the treatment of previously deposited precursors (titanium oxide, strontium nitrate, or barium nitrite) in a water fluid medium at 400°C. The obtained samples are characterized by X-ray powder diffraction (XRD) analysis and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) spectroscopy. It is found that, in the presence of titanium oxide, α-Al2O3 is partially hydrated to form basic aluminum hydroxide AlO(OH) (boehmite), which is not detected by XRD after the treatment of α-Al2O3 in a water fluid. SEM with EDX spectroscopy demonstrates that strontium ions under the conditions of the treatment in a water fluid preferably interact with titanium oxide to form SrTiO3, although the aluminum oxide content in the samples is much higher. The conditions are determined for obtaining systems with different spatial distributions of the supported component inside the granules of the support by varying the procedure of its preliminary impregnation with the titanium oxide precursor.