ALKALI-METAL BETA AND BETA ALUMINA AND GALLATE POLYCRYSTALLINE CERAMICS AND FABRICATION BY A VAPOR PHASE METHOD

摘要

A ceramic composite containing alkali-metal- beta - or beta ''-alumina and an oxygen-ion conductor is fabricated by converting alpha -alumina to alkali-metal- beta - or beta ''-alumina. A ceramic composite with continuous phases of alpha -alumina and the oxygen-ion conducting ceramic, such as zirconia, is exposed to a vapor containing an alkali-metal oxide, such as an oxide of sodium or potassium. Alkali metal ions diffuse through alkali-metal- beta - or beta ''-alumina converted from alpha -alumina and oxygen ions diffuse through the oxygen-ion conducting ceramic to a reaction front where alpha -alumina is converted to alkali-metal- beta - or beta ''-alumina. A stabilizer for alkali-metal- beta ''-alumina is preferably introduced into the alpha -alumina/oxygen-ion conductor composite or introduced into the vapor used to convert the alpha -alumina to an alkali-metal- beta ''-alumina.