A Novel Reaction Path to BaTiO 3 by the Oxidation of a Solid Metallic Precursor

Multilayer capacitors with thin, dielectric BaTiO 3 layers can possess a relatively high capacitance per unit volume. A solid metallic precursor method has recently been developed for preparing thin BaTiO 3 /noble metal laminates. In the present paper, the phase and microstructural evolution of Ba‐Ti metallic precursors were examined after oxidation at 300° to 900°C in pure oxygen at 1 atm pressure. Barium peroxide, BaO 2 , formed rapidly during oxidation at 300°C, with titanium largely remaining as unoxidized particles in the peroxide matrix. Between 375° and 500°C, the solidstate reaction of barium peroxide with metallic titanium yielded barium orthotitanate, Ba 2 TiO 4 . Further exposure to temperatures between 500° and 900°C resulted in the oxidation of residual metallic titanium. The oxidized titanium then reacted with the orthotitanate matrix to form barium metatitanate, BaTiO 3 . The rate of formation of BaTiO 3 was found to be strongly dependent on the degree of milling of the Ba‐Ti precursors and on the heating rate between 300° and 500°C.