Crystallization kinetics of Ba0.8Sr0.2TiO3 sols and sol-gel synthesis of Ba0.8Sr0.2TiO3 thin films

Chemically homogeneous Ba0.8Sr0.2TiO3 (BST) sols were synthesized using barium acetate, strontium acetate, and titanium tetra-n-butoxide as starting materials. The crystallization behaviour of the BST sols and thin films was studied by differential thermal analysis (DTA) and X-ray diffraction (XRD). The kinetics of crystallization was studied by applying the DTA measurement carried out at different heating rates. The effective activation energy of crystallization associated with the formation of perovskite phase was measured as 270.8 kJ mol(-1). The Avrami exponent n (reaction order) is about 1, which suggests that the growth of perovskite phase is diffusion-controlled The calculated half-life time indicates that the minimum temperature for the crystallization is 600 degrees C. The BST thin films were prepared on Pt-coated silicon substrates from the sols. The films annealed at 650 degrees C have good perovskite crystallinity without the existence of second phase. (C) 1999 Elsevier Science Limited and Techna S.r.l. All rights reserved.