Preparation and properties of (Ba0.7Sr0.3)TiO3 powders and thin films using precursor solutions formed from alkoxide-hydroxide

(Ba0.7Sr0.3) TiO3 powders and thin films were prepared using alkoxide-hydro oxide route. Solutions of Ba and Sr hydroxides dissolved in methanol were reacted with Ti-isopropoxide under conditions of stirring at room temperature for 15 h, and then dried under reduced pressure at less than or equal to 40 degrees C to prepare precursors of (Ba0.7Sr0.3) TiO3 powder. The amorphous precursors were hydrolyzed at 100 degrees C by introducing nitrogen gas containing water vapor. The hydrolyzed products were crystalline nanosize powders of (Ba0.7Sr0.3) TiO3 As-hydrolyzed (Ba0.7Sr0.3) TiO3 powders showed a good crystallinity with cubic phase. (Ba0.7Sr0.3) TiO3 thin films were also successfully prepared at 650 degrees C on Pt/Ti/SiO2/Si substrates from precursor solutions obtained by the reaction of alkoxide with hydroxides. The (Ba0.7Sr0.3) TiO3 thin films exhibited the microstructure with fine grains as small as 20-60 nm. The dielectric constants of the thin films ranged from 600 to 800 at room temperature. (C) 1999 Elsevier Science Limited. All rights reserved.