Porous behavior and dielectric properties of barium strontium titanate synthesized by sol-gel method in the presence of triethanolamine

This investigation presents a novel method of preparation of barium strontium titanate (BST) from [Ba(2,4-pentadionate)-Sr(2,4-pentadionate)-Ti(OC3H7)(4)-TEA-i-PrOH-water] system. Triethanolamine (TEA) was used as an additive, which prevents the precipitation of oxides from the alcoholic titanium isopropoxide solution in the presence of excess water. An increasing molar ratio of mater from 4.5 to 6.5 did not show any precipitation in the precursor sols in the presence of triethanolamine. Thermal behavior of the xerogel was studied by thermal gravimetric analysis (TGA). X-ray diffraction (XRD) indicated that the pure BST phase was crystallized at 900 degrees C. Triethanolamine was observed to influence the porous behavior of the final powders. Pore diameter of the powder calcined at 900 degrees C, was increased from 0.013 mu m to 0.080 mu m when the molar ratio of triethanolamine increased from zero to four. Therefore, a porous powder of BST was obtained at a higher molar ratio of triethanolamine. Porous behavior was also studied with respect to water and heat treatment, and explained with the help of density measurements and scanning electron microscopy (SEM). A low dielectric constant was obtained for the highly porous BST as compared with the high value for dense material.