Processing of Functional Ceramics by Metallorganic Route

Abstract

Functional ceramics with controlled microstructure were successfully synthesized through metallorganics. The controlled hydrolysis of metal alkoxides yields BaO-TiO2 powders, which could be sintered to the microwave dielectrics of improved properties. Zirconia toughened ceramics were fabricated by a novel processing using zirconia-coated composite powders of silica or mullite synthesized via cohydrolysis of zirconium alkoxide on dispersed starting powders. Zirconia-mullite composite powders were sintered affording compacts dispersed uniformly with zirconia particles, which showed the increased fracture toughness and designed microstructure. The controlled hydrolysis of lithium and niobium alkoxides was found to form the double alkoxide in a solution, which was converted to stoichiometric LiNbO3 powders, films and fibers. Crystalline, epitaxial LiNbO3 films with stoichiometry were prepared on sapphire substrate at 250°C. The orientation and crystallinity of LiNbO3 films could be controlled by the selection of the crystallographic plane of a substrate as well as the crystallization conditions. Carbon of controlled morphology dispersed with finely metal or metallic compound particles can be synthesized in high carbon yield by the pressure pyrolysis of organometallic polymers. Magnetite-dispersed spherulitic carbon was synthesized from organoiron copolymer-water system. This paper describes the results and features of the ceramic processing through metallorganics.