Electrical properties of sodium beta-alumina ceramics synthesized by citrate sol-gel route using glycerine

Sodium beta-alumina is an efficient ion conducting solid electrolyte due to fast ionic conductivity arising from its favourable crystal structure. Other main requirements of a material to serve as solid electrolyte are fine grain structure, minimum porosity and good electrical properties at the operating temperature, which is usually about 300 degrees C. Mg-doped sodium beta-alumina powder was synthesized using citrate sol-gel route (wherein glycerine was used as a fuel) and calcined at different temperatures (950-1100 degrees C). The synthesized powders have beta ''-alumina as a dominant phase and particle size in range 75-95 nm. The obtained powders were compacted by uniaxial pressing at 100 MPa and sintered at 1500 degrees C for 3-10 h. Maximal density of the sintered samples was 92% TD and the primary phase was beta ''-alumina. The highest conductivity of 0.38 S/cm was measured at 300 degrees C and the lowest activation energy for conduction of 0.20 eV was obtained.