CHEMICAL-PROCESSING AND DENSIFICATION CHARACTERISTICS OF LITHIUM ALUMINOSILICATE (LAS) GELS

Abstract

Two different chemical processing routes were successfully used for the fabrication of lithium aluminosilicate (LAS) specimens having dense and homogeneous microstructure with an essentially pore-free state. These are (i) sol-gel route using the hydrolysis-condensation reaction of metal alkoxides and (ii) mixed colloidal processing route. Lowering Li content in the sol-gel-derived LAS significantly enhanced densification and retarded the crystallization. The beta-spodumene (approximately 0.8-mu-m) seeding in the sol-gel-derived LAS modified the sequence of phase transformations and lowered the crystallization temperature by 120-degrees-C. Therefore, combining the epitaxial seeding with the sol-gel process, one can bring down the crystallization temperature to the sintering temperature range (approximately 800-degrees-C). Similarly, the LAS gel prepared by the mixed colloidal processing route exhibited a noticeable shrinkage over a broad temperature range (600-950-degrees-C) and produced a dense sintered body with an essentially pore-free microstructure.