β-Alumina’s layered crystal structure makes it an excellent ion conductor that is stable in corrosive, reducing and oxidative environments. Because of these properties it is ideal for many electrochemical applications, including: sodium sulfur batteries, alkali metal thermo electric converters (AMTEC), sodium heat engines (SHE), and sodium-nickel chloride (Zebra) batteries.
MSRI has developed a novel process for the fabrication of composite materials containing sodium, potassium, or rubidium β"- and ”-alumina. By fabricating these materials at relatively low temperatures (1400-1450° C), MSRI’s patented process avoids the formation of a transient liquid state. The presence of the remnant liquid phases at grain boundaries renders materials made by conventional processes susceptible to water attack.
Materials made using MSRI’s process result in two phases: zirconia (white) and β”-alumina (dark). The inclusion of zirconia improves the strength of the material compared to conventional fabrication.