BARIUM-TITANATE NOBLE-METAL LAMINATES PREPARED BY THE OXIDATION OF SOLID METALLIC PRECURSORS

A novel and attractive method for preparing multicomponent electronic ceramics and ceramic-metal composites is the oxidation of solid metallic precursors (SMP). This metallurgical processing route consists of the following steps: (i) preparation of a solid metallic precursor containing the proper ratio of elements for the final ceramic or ceramic-metal composite, (ii) compaction and forming of the metallic precursor into a desired shape, and (iii) oxidation to produce a monolithic ceramic or ceramic-metal composite. While the SMP method has been used to prepare wires and tapes containing a variety of superconducting oxides, this method has not been widely used to synthesize other electronic ceramics. In this paper, the synthesis of dielectric BaTiO3/noble metal laminates from solid metallic precursors is discussed. Ba-Ti precursor powders have been produced by solid-state mechanical alloying. The precursor powder was sealed inside noble metal tubes and rolled to form thin Ba-Ti/noble metal laminates. Exposure of the Ba-Ti core in such tapes to temperatures greater-than-or-equal-to 300-degrees-C in pure oxygen resulted in rapid oxidation. Post-oxidation annealing at elevated temperatures (greater-than-or-equal-to 900-degrees-C) yielded dielectric BaTiO3/Ag or BaTiO3/Pd laminates.