Synthesis of Ba_xSr_1-xTiO₃ thin films from complex alkoxide solutions

High dielectric barium-strontium-titanate (Ba_0.5Sr_0.5)TiO₃ (BST) thin films were fabricated by a spincoating technique. The fabrication process consisted of three steps. First, a complex alkoxide was synthesized from barium, strontium and Ti-alkoxide (titanium tetraethoxide) in 2-methoxyethanol at 125°C for 3h. Then, hydrolysis and condensation reactions of the complex alkoxide were carried out at 75°C in 2-methoxyethanol containing nitric acid as a catalysis. Finally, the sols obtained by hydrolysis and condensation of Ba-Sr-Ti complex alkoxide were casted onto glass substrates. The films were subjected to heat treatment at temperatures between 350 and 900°C. The films started to crystallize into a perovskite structure BST at 500°C, and were well-crystallized at 525-550°C. The BST films that were heat-treated at 550°C had dielectric constant exceeding 2000 at 800 Hz.