Synthesis of /spl beta/"-Al/sub 2/O/sub 3/ polymer precursor and its pyrolysis to ultrafine /spl beta/"-Al/sub 2/O/sub 3/ powders [AMTEC applications]

/spl beta/"-alumina, an important high-temperature solid electrolyte for alkali metal thermoelectric conversion (AMTEC) applications, was synthesized in ultrafine particle form from inexpensive starting materials via a polymeric, metalloorganic precursor. The precursor, made by reacting NaOH, LiOH, and Al(OH)/sub 3/ with triethanolamine (TEA) in ethylene glycol (EG) while distilling off product water, is a glassy thermoplastic at room temperature, and dissolves in polar solvents, e.g. ethanol. Spheroidal, nonagglomerated particles of <100 nm diameter were formed by flame-spray pyrolysis of ethanolic solutions of the precursor. X-ray powder diffraction showed the as-formed powders to be an intermediate phase which transforms to /spl beta/"-alumina upon heating above 1000/spl deg/C.