PHASE-FORMATION KINETICS OF XEROGEL AND ELECTRICAL-PROPERTIES OF SOL-GEL-DERIVED BA2SR1-XTIO3 THIN-FILMS

Chemically homogeneous BaxSr1-xTiO3 (BST with x=0.6) multicomponent so l was synthesized using barium oxide, strontium chloride, and Ti-alkox ide (titanium isopropoxide) as starting materials. Acetylacetone (AcAc ) was introduced as a chelating agent to reduce a rapid hydrolysis rat e of Ti-alkoxide. Analysis of Fourier transform infrared spectroscopy (FTIR) spectra indicated that the stabilization of: BST sols was achie ved by the chelation of Ti-alkoxide with the enolic form of AcAc. The effective activation energy associated with the formation of perovskit e phase from the xerogel was estimated by the differential thermal ana lysis (DTA) experiment using various heating rates. It is approximatel y 400 kJ/mol with the Avrami exponent (reaction order) of n=1, suggest ing that the growth of perovskite BST is diffusion-controlled. 'The ca lculated half-life time suggests that the minimum temperature for the crystallization which is practically accessible to a real processing i s approximately 600 degrees C. The BST thin film fabricated on the ''P t(150 nm)/Ti(100 nm)/SiO2(100 nm)/Si'', substrate exhibited the relati ve dielectric permittivity of 310 and can be represented by an equival ent circuit consisting of a resistive component originated from the bu lk perovskite grain and a. parallel RC component resulting from the pr esence of the grain boundary.