Materials and Systems Research, Inc.

Jan-Fong Jue

Anil Vasudeo Virkar

Kuan-Zong Fung

A ceramic composite containing alkali-metal-beta- or beta&Prime;-alumina and an oxygen-ion conductor is fabricated by converting alpha-alumina to alkali-metal-beta- or beta&Prime;-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&Prime;-alumina converted from &agr;-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&Prime;-alumina. A stabilizer for alkali-metal-beta&Prime;-alumina is preferably introduced into the &agr;-alumina/oxygen-ion conductor composite or introduced into the vapor used to convert the alpha-alumina to an alkali-metal-beta&Prime;-alumina.

Alkali-metal-beta-and beta&Prime;-alumina and gallate polycrystalline ceramics and fabrication by a vapor phase method

A ceramic composite containing alkali-metal-&bgr;- or &bgr;&Prime;-alumina and an oxygen-ion conductor is fabricated by converting &agr;-alumina to alkali-metal-&bgr;- or &bgr;&Prime;-alumina. A ceramic composite with continuous phases of &agr;-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-&bgr;- or &bgr;&Prime;-alumina converted from &agr;-alumina and oxygen ions diffuse through the oxygen-ion conducting ceramic to a reaction front where &agr;-alumina is converted to alkali-metal-&bgr;- or &bgr;&Prime;-alumina. A stabilizer for alkali-metal-&bgr;&Prime;-alumina is preferably introduced into the &agr;-alumina/oxygen-ion conductor composite or introduced into the vapor used to convert the &agr;-alumina to an alkali-metal-&bgr;&Prime;-alumina.

Alkali-metal-&bgr;- and &bgr;&Prime;-alumina and gallate polycrystalline ceramics and fabrication by a vapor phase method

A t&prime;-phase zirconia shapes with superior properties are made by forming a zirconia powder containing a rare-earth-oxide dopant into sintered bodies. The sintered bodies are heat treated in an oxygen atmosphere at a temperature high enough to form a cubic phase. The heated body is then cooled rapidly to form a t&prime;-phase. The t&prime;-phase is characterized with a large grain size, is resistant to transformation, low temperature degradation, and has excellent toughness, and creep resistance. Rare earth-oxide dopants include yttria, scandia, erbia, and ceria. For yttria doped materials, the sintered body is doped with between 2.5 and 5 mole percent yttria.

t&prime;-phase zirconias for high temperature applications

Method for forming t'-phase zirconia for high temperature applications

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.

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Salt Lake City, UT, United States of America

Jan-Fong Jue