New precursors for direct synthesis of single phase Na- and K-β"-aluminas for use in AMTEC systems

Alkali metal thermoelectric converters (AMTEC) are efficient direct energy conversion devices that depend on the use of highly conductive beta-alumina membranes for their operation. The key component of the AMTEC system is a highly conductive Na-β"-alumina solid electrolyte which conducts sodium ions from the high to low temperature zone, thereby generating electricity. AMTEC cells convert thermal to electrical energy by using heat to produce and maintain an alkali metal concentration gradient across the ion transporting BASE membrane. The authors have developed a method for producing pure phase Na-β"-alumina and K-β"-alumina powders from single phase nano-sized carboxylato-alumoxanes precursors. Sodium or potassium ions (the mobile ions) and either Mg²⁺ or Li⁺ ions (which stabilize the β"-alumina structure) can be atomically dispersed into the carboxylato-alumoxane lattice at low (<100°C) temperature. Calcination of the carboxylato-alumoxane precursors at 1200-1500°C produces pure phase β"-alumina powders