A NOVEL REACTION-PATH TO BATIO3 BY THE OXIDATION OF A SOLID METALLIC PRECURSOR

Multilayer capacitors with thin, dielectric BaTiO3 layers can possess a relatively high capacitance per unit volume. A solid metallic precur sor method has recently been developed for preparing thin BaTiO3/noble metal laminates. In the present paper, the phase and microstructural evolution of Ba-Ti metallic precursors were examined after oxidation a t 300-degrees to 900-degrees-C in pure oxygen at 1 atm pressure. Bariu m peroxide, BaO2, formed rapidly during oxidation at 300-degrees-C, wi th titanium largely remaining as unoxidized particles in the peroxide matrix. Between 375-degrees and 500-degrees-C, the solid-state reactio n of barium peroxide with metallic titanium yielded barium orthotitana te, Ba2TiO4. Further exposure to temperatures between 500-degrees and 900-degrees-C resulted in the oxidation of residual metallic titanium. The oxidized titanium then reacted with the orthotitanate matrix to f orm barium metatitanate, BaTiO3. The rate of formation of BaTiO3 was f ound to be strongly dependent on the degree of milling of the Ba-Ti pr ecursors and on the heating rate between 300-degrees and 500-degrees-C .